Method for performing random access procedure and device therefor

ABSTRACT

The present disclosure provides a method for receiving a physical downlink shared channel (PDSCH) by a terminal in a wireless communication system. Specifically, the method may comprise: transmitting a physical random access channel (PRACH); monitoring a downlink control channel (DCI) for scheduling a PDSCH related to the PRACH; and receiving the PDSCH on the basis of the DCI, wherein the DCI is detected on the basis of a radio network temporary identifier (RNTI).

This application is the Continuation Bypass of International ApplicationNo. PCT/KR2021/002148 filed on Feb. 19, 2021, which claims the benefitof Korean Patent Application Nos. 10-2020-0021881 filed on Feb. 21, 2020and 10-2020-0044260 filed on Apr. 10, 2020, the contents of which areall hereby incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present disclosure relates to a method of performing a random accessprocedure and apparatus therefor, and more particularly, a method ofperforming a two-step random access procedure (Type-2 random accessprocedure) by a user equipment (UE) and apparatus therefor.

BACKGROUND ART

As more and more communication devices demand larger communicationtraffic along with the current trends, a future-generation 5thgeneration (5G) system is required to provide an enhanced wirelessbroadband communication, compared to the legacy LTE system. In thefuture-generation 5G system, communication scenarios are divided intoenhanced mobile broadband (eMBB), ultra-reliability and low-latencycommunication (URLLC), massive machine-type communication (mMTC), and soon.

Herein, eMBB is a future-generation mobile communication scenariocharacterized by high spectral efficiency, high user experienced datarate, and high peak data rate, URLLC is a future-generation mobilecommunication scenario characterized by ultra-high reliability,ultra-low latency, and ultra-high availability (e.g., vehicle toeverything (V2X), emergency service, and remote control), and mMTC is afuture-generation mobile communication scenario characterized by lowcost, low energy, short packet, and massive connectivity (e.g., Internetof things (IoT)).

DISCLOSURE Technical Problem

The object of the present disclosure is to provide a method ofperforming a random access procedure and apparatus therefor.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present disclosure are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present disclosure could achieve will be more clearlyunderstood from the following detailed description.

Technical Solution

In an aspect of the present disclosure, there is provided a method ofreceiving a physical downlink shared channel (PDSCH) by a user equipment(UE) in a wireless communication system. The method may include:transmitting a physical random access channel (PRACH); monitoringdownlink control information (DCI) for scheduling a PDSCH related to thePRACH; and receiving the PDSCH based on the DCI, based on the DCI beingdetected based on a radio network temporary identifier (RNTI).

In this case, the PDSCH is received regardless of whether two bits for afirst system frame number (SFN) included in the DCI are identical to twobits for a second SFN in which the PRACH is transmitted.

Additionally, based on the UE being incapable of checking whether twobits for a first system frame number (SFN) included in the DCI areidentical to two bits for a second SFN in which the PRACH istransmitted, the PDSCH is received based on the DCI.

Additionally, based on the UE being capable of checking whether two bitsfor a first system frame number (SFN) included in the DCI are identicalto two bits for a second SFN in which the PRACH is transmitted and theUE confirming that the two bits for the first SFN are not identical tothe two bits for the second SFN, the PDSCH is not received.

Additionally, based on the UE being capable of checking whether two bitsfor a first system frame number (SFN) included in the DCI are identicalto two bits for a second SFN in which the PRACH is transmitted and theUE confirming that the two bits for the first SFN are identical to thetwo bits for the second SFN, the PDSCH is received based on the DCI.

Additionally, a length of a monitoring window for the DCI may exceed 10ms.

Additionally, the RNTI is a MsgB-RNTI.

In another aspect of the present disclosure, there is provided a UEconfigured to receive a PDSCH in a wireless communication system. The UEmay include: at least one transceiver; at least one processor; and atleast one memory operably connected to the at least one processor andconfigured to store instructions that, when executed, cause the at leastone processor to perform operations. The operations may include:transmitting a physical random access channel (PRACH) through the atleast one transceiver; monitoring downlink control information (DCI) forscheduling a PDSCH related to the PRACH; and receiving the PDSCH basedon the DCI through the at least one transceiver, based on the DCI beingdetected based on a radio network temporary identifier (RNTI).

In this case, the PDSCH is received regardless of whether two bits for afirst system frame number (SFN) included in the DCI are identical to twobits for a second SFN in which the PRACH is transmitted.

Additionally, based on the UE being incapable of checking whether twobits for a first system frame number (SFN) included in the DCI areidentical to two bits for a second SFN in which the PRACH istransmitted, the PDSCH is received based on the DCI.

Additionally, based on the UE being capable of checking whether two bitsfor a first system frame number (SFN) included in the DCI are identicalto two bits for a second SFN in which the PRACH is transmitted and theUE confirms that the two bits for the first SFN are not identical to thetwo bits for the second SFN, the PDSCH is not received.

Additionally, based on the UE being capable of checking whether two bitsfor a first system frame number (SFN) included in the DCI are identicalto two bits for a second SFN in which the PRACH is transmitted and theUE confirms that the two bits for the first SFN are identical to the twobits for the second SFN, the PDSCH is received based on the DCI.

Additionally, a length of a monitoring window for the DCI may exceed 10ms.

Additionally, the RNTI may be a MsgB-RNTI.

In a further aspect of the present disclosure, there is provided anapparatus configured to receive a PDSCH in a wireless communicationsystem. The apparatus may include: at least one processor; and at leastone memory operably connected to the at least one processor andconfigured to store instructions that, when executed, cause the at leastone processor to perform operations. The operations may include:transmitting a physical random access channel (PRACH); monitoringdownlink control information (DCI) for scheduling a PDSCH related to thePRACH; and receiving the PDSCH based on the DCI, based on the DCI beingdetected based on a radio network temporary identifier (RNTI).

Advantageous Effects

According to the present disclosure, when a user equipment (UE) does notknow the index of a system frame number (SFN) for transmitting aphysical random access channel (PRACH) or does not interpret the indexof an SFN included in received downlink control information (DCI) toreduce delay caused by decoding of the DCI, the UE may efficientlyperform a 2-step random access procedure (Type-2 random accessprocedure).

It will be appreciated by persons skilled in the art that the effectsthat could be achieved with the present disclosure are not limited towhat has been particularly described hereinabove and other advantages ofthe present disclosure will be more clearly understood from thefollowing detailed description.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating physical channels and a general signaltransmission method using the physical channels in a 3GPP system.

FIGS. 2, 3 and 4 are diagrams illustrating structures of a radio frameand slots used in a new RAT (NR) system.

FIGS. 5, 6, 7, 8, 9 and 10 are diagrams illustrating the composition ofa synchronization signal/physical broadcast channel (SS/PBCH) block anda method of transmitting an SS/PBCH block.

FIG. 11 is a diagram illustrating an exemplary 4-step random accesschannel (RACH) procedure.

FIG. 12 is a diagram illustrating an exemplary 2-step RACH procedure.

FIG. 13 is a diagram illustrating an exemplary contention-free RACHprocedure.

FIG. 14 is a diagram illustrating synchronization signal (SS) blocktransmission and physical random access channel (PRACH) resources linkedto SS blocks.

FIG. 15 is a diagram illustrating SS block transmission and PRACHresources linked to SS blocks.

FIG. 16 is a diagram illustrating exemplary RACH occasionconfigurations.

FIGS. 17 to 19 are diagrams for explaining operations of a userequipment (UE) and a base station (BS) according to embodiments of thepresent disclosure.

FIGS. 20 to 22 are diagrams for explaining methods of monitoringdownlink control information (DCI) for message B (MsgB) transmissionaccording to embodiments of the present disclosure.

FIG. 23 illustrates an example of a communication system to whichembodiments of the present disclosure are applied.

FIGS. 24 to 27 illustrate examples of various wireless devices to whichembodiments of the present disclosure are applied.

BEST MODE

The configuration, operation, and other features of the presentdisclosure will readily be understood with embodiments of the presentdisclosure described with reference to the attached drawings.Embodiments of the present disclosure as set forth herein are examplesin which the technical features of the present disclosure are applied toa 3rd generation partnership project (3GPP) system.

While embodiments of the present disclosure are described in the contextof long term evolution (LTE) and LTE-advanced (LTE-A) systems, they arepurely exemplary. Therefore, the embodiments of the present disclosureare applicable to any other communication system as long as the abovedefinitions are valid for the communication system.

The term, base station (BS) may be used to cover the meanings of termsincluding remote radio head (RRH), evolved Node B (eNB or eNode B),transmission point (TP), reception point (RP), relay, and so on.

The 3GPP communication standards define downlink (DL) physical channelscorresponding to resource elements (REs) carrying information originatedfrom a higher layer, and DL physical signals which are used in thephysical layer and correspond to REs which do not carry informationoriginated from a higher layer. For example, physical downlink sharedchannel (PDSCH), physical broadcast channel (PBCH), physical multicastchannel (PMCH), physical control format indicator channel (PCFICH),physical downlink control channel (PDCCH), and physical hybrid ARQindicator channel (PHICH) are defined as DL physical channels, andreference signals (RSs) and synchronization signals (SSs) are defined asDL physical signals. An RS, also called a pilot signal, is a signal witha predefined special waveform known to both a gNode B (gNB) and a userequipment (UE). For example, cell specific RS, UE-specific RS (UE-RS),positioning RS (PRS), and channel state information RS (CSI-RS) aredefined as DL RSs. The 3GPP LTE/LTE-A standards define uplink (UL)physical channels corresponding to REs carrying information originatedfrom a higher layer, and UL physical signals which are used in thephysical layer and correspond to REs which do not carry informationoriginated from a higher layer. For example, physical uplink sharedchannel (PUSCH), physical uplink control channel (PUCCH), and physicalrandom access channel (PRACH) are defined as UL physical channels, and ademodulation reference signal (DMRS) for a UL control/data signal, and asounding reference signal (SRS) used for UL channel measurement aredefined as UL physical signals.

In the present disclosure, the PDCCH/PCFICH/PHICH/PDSCH refers to a setof time-frequency resources or a set of REs, which carry downlinkcontrol information (DCI)/a control format indicator (CFI)/a DLacknowledgement/negative acknowledgement (ACK/NACK)/DL data. Further,the PUCCH/PUSCH/PRACH refers to a set of time-frequency resources or aset of REs, which carry UL control information (UCI)/UL data/a randomaccess signal. In the present disclosure, particularly a time-frequencyresource or an RE which is allocated to or belongs to thePDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH is referred to as a PDCCHRE/PCFICH RE/PHICH RE/PDSCH RE/PUCCH RE/PUSCH RE/PRACH RE or a PDCCHresource/PCFICH resource/PHICH resource/PDSCH resource/PUCCHresource/PUSCH resource/PRACH resource. Hereinbelow, if it is said thata UE transmits a PUCCH/PUSCH/PRACH, this means that UCI/UL data/a randomaccess signal is transmitted on or through the PUCCH/PUSCH/PRACH.Further, if it is said that a gNB transmits a PDCCH/PCFICH/PHICH/PDSCH,this means that DCI/control information is transmitted on or through thePDCCH/PCFICH/PHICH/PDSCH.

Hereinbelow, an orthogonal frequency division multiplexing (OFDM)symbol/carrier/subcarrier/RE to which a CRS/DMRS/CSI-RS/SRS/UE-RS isallocated to or for which the CRS/DMRS/CSI-RS/SRS/UE-RS is configured isreferred to as a CRS/DMRS/CSI-RS/SRS/UE-RS symbol/carrier/subcarrier/RE.For example, an OFDM symbol to which a tracking RS (TRS) is allocated orfor which the TRS is configured is referred to as a TRS symbol, asubcarrier to which a TRS is allocated or for which the TRS isconfigured is referred to as a TRS subcarrier, and an RE to which a TRSis allocated or for which the TRS is configured is referred to as a TRSRE. Further, a subframe configured to transmit a TRS is referred to as aTRS subframe. Further, a subframe carrying a broadcast signal isreferred to as a broadcast subframe or a PBCH subframe, and a subframecarrying a synchronization signal (SS) (e.g., a primary synchronizationsignal (PSS) and/or a secondary synchronization signal (SSS)) isreferred to as an SS subframe or a PSS/SSS subframe. An OFDMsymbol/subcarrier/RE to which a PSS/SSS is allocated or for which thePSS/SSS is configured is referred to as a PSS/SSS symbol/subcarrier/RE.

In the present disclosure, a CRS port, a UE-RS port, a CSI-RS port, anda TRS port refer to an antenna port configured to transmit a CRS, anantenna port configured to transmit a UE-RS, an antenna port configuredto transmit a CSI-RS, and an antenna port configured to transmit a TRS,respectively. Antenna port configured to transmit CRSs may bedistinguished from each other by the positions of REs occupied by theCRSs according to CRS ports, antenna ports configured to transmit UE-RSsmay be distinguished from each other by the positions of REs occupied bythe UE-RSs according to UE-RS ports, and antenna ports configured totransmit CSI-RSs may be distinguished from each other by the positionsof REs occupied by the CSI-RSs according to CSI-RS ports. Therefore, theterm CRS/UE-RS/CSI-RS/TRS port is also used to refer to a pattern of REsoccupied by a CRS/UE-RS/CSI-RS/TRS in a predetermined resource area.

FIG. 1 illustrates physical channels and a general method fortransmitting signals on the physical channels in the 3GPP system.

Referring to FIG. 1, when a UE is powered on or enters a new cell, theUE performs initial cell search (S201). The initial cell search involvesacquisition of synchronization to an eNB. Specifically, the UEsynchronizes its timing to the eNB and acquires a cell identifier (ID)and other information by receiving a primary synchronization channel(P-SCH) and a secondary synchronization channel (S-SCH) from the eNB.Then the UE may acquire information broadcast in the cell by receiving aphysical broadcast channel (PBCH) from the eNB. During the initial cellsearch, the UE may monitor a DL channel state by receiving a downlinkreference signal (DL RS).

After the initial cell search, the UE may acquire detailed systeminformation by receiving a physical downlink control channel (PDCCH) andreceiving a physical downlink shared channel (PDSCH) based oninformation included in the PDCCH (S202).

If the UE initially accesses the eNB or has no radio resources forsignal transmission to the eNB, the UE may perform a random accessprocedure with the eNB (S203 to S206). In the random access procedure,the UE may transmit a predetermined sequence as a preamble on a physicalrandom access channel (PRACH) (S203 and S205) and may receive a responsemessage to the preamble on a PDCCH and a PDSCH associated with the PDCCH(S204 and S206). In the case of a contention-based RACH, the UE mayadditionally perform a contention resolution procedure.

After the above procedure, the UE may receive a PDCCH and/or a PDSCHfrom the eNB (S207) and transmit a physical uplink shared channel(PUSCH) and/or a physical uplink control channel (PUCCH) to the eNB(S208), which is a general DL and UL signal transmission procedure.Particularly, the UE receives downlink control information (DCI) on aPDCCH. Herein, the DCI includes control information such as resourceallocation information for the UE. Different DCI formats are definedaccording to different usages of DCI.

Control information that the UE transmits to the eNB on the UL orreceives from the eNB on the DL includes a DL/UL acknowledgment/negativeacknowledgment (ACK/NACK) signal, a channel quality indicator (CQI), aprecoding matrix index (PMI), a rank indicator (RI), etc. In the 3GPPLTE system, the UE may transmit control information such as a CQI, aPMI, an RI, etc. on a PUSCH and/or a PUCCH.

The use of an ultra-high frequency band, that is, a millimeter frequencyband at or above 6 GHz is under consideration in the NR system totransmit data in a wide frequency band, while maintaining a hightransmission rate for multiple users. The 3GPP calls this system NR. Inthe present disclosure, the system will also be referred to as an NRsystem.

The NR system adopts the OFDM transmission scheme or a similartransmission scheme. Specifically, the NR system may use OFDM parametersdifferent from those in LTE. Further, the NR system may follow thelegacy LTE/LTE-A numerology but have a larger system bandwidth (e.g.,100 MHz). Further, one cell may support a plurality of numerologies inthe NR system. That is, UEs operating with different numerologies maycoexist within one cell.

FIG. 2 illustrates a structure of a radio frame used in NR.

In NR, UL and DL transmissions are configured in frames. The radio framehas a length of 10 ms and is defined as two 5-ms half-frames (HF). Thehalf-frame is defined as five 1 ms subframes (SF). A subframe is dividedinto one or more slots, and the number of slots in a subframe depends onsubcarrier spacing (SCS). Each slot includes 12 or 14 OFDM(A) symbolsaccording to a cyclic prefix (CP). When a normal CP is used, each slotincludes 14 symbols. When an extended CP is used, each slot includes 12symbols. Here, the symbols may include OFDM symbols (or CP-OFDM symbols)and SC-FDMA symbols (or DFT-s-OFDM symbols).

[Table 1] illustrates that the number of symbols per slot, the number ofslots per frame, and the number of slots per subframe vary according tothe SCS when the normal CP is used.

TABLE 1 SCS (15 * 2{circumflex over ( )}u) N^(slot) _(symb) N^(frame,u)_(slot) N^(subframe,u) _(slot)  15 KHz (u = 0) 14 10 1  30 KHz (u = 1)14 20 2  60 KHz (u = 2) 14 40 4 120 KHz (u = 3) 14 80 8 240 KHz (u = 4)14 160 16 * N^(slot) _(symb): Number of symbols in a slot * N^(frame,u)_(slot): Number of slots in a frame * N^(subframe,u) _(slot): Number ofslots in a subframe

[Table 2] illustrates that the number of symbols per slot, the number ofslots per frame, and the number of slots per subframe vary according tothe SCS when the extended CP is used.

TABLE 2 SCS (15 * 2{circumflex over ( )}u) N^(slot) _(symb) N^(frame,u)_(slot) N^(subframe,u) _(slot) 60 KHz (u = 2) 12 40 4

In the NR system, the OFDM(A) numerology (e.g., SCS, CP length, etc.)may be configured differently among a plurality of cells merged for oneUE. Thus, the (absolute time) duration of a time resource (e.g., SF,slot or TTI) (referred to as a time unit (TU) for simplicity) composedof the same number of symbols may be set differently among the mergedcells.

FIG. 3 illustrates a slot structure of an NR frame. A slot includes aplurality of symbols in the time domain. For example, in the case of thenormal CP, one slot includes seven symbols. On the other hand, in thecase of the extended CP, one slot includes six symbols. A carrierincludes a plurality of subcarriers in the frequency domain. A resourceblock (RB) is defined as a plurality of consecutive subcarriers (e.g.,12 consecutive subcarriers) in the frequency domain. A bandwidth part(BWP) is defined as a plurality of consecutive (P)RBs in the frequencydomain and may correspond to one numerology (e.g., SCS, CP length,etc.). A carrier may include up to N (e.g., five) BWPs. Datacommunication is performed through an activated BWP, and only one BWPmay be activated for one UE. In the resource grid, each element isreferred to as a resource element (RE), and one complex symbol may bemapped thereto.

FIG. 4 illustrates a structure of a self-contained slot. In the NRsystem, a frame has a self-contained structure in which a DL controlchannel, DL or UL data, a UL control channel, and the like may all becontained in one slot. For example, the first N symbols (hereinafter, DLcontrol region) in the slot may be used to transmit a DL controlchannel, and the last M symbols (hereinafter, UL control region) in theslot may be used to transmit a UL control channel N and M are integersgreater than or equal to 0. A resource region (hereinafter, a dataregion) that is between the DL control region and the UL control regionmay be used for DL data transmission or UL data transmission. Forexample, the following configuration may be considered. Respectivesections are listed in a temporal order.

1. DL only configuration

2. UL only configuration

3. Mixed UL-DL configuration

-   -   DL region+Guard period (GP)+UL control region    -   DL control region+GP+UL region    -   * DL region: (i) DL data region, (ii) DL control region+DL data        region    -   * UL region: (i) UL data region, (ii) UL data region+UL control        region

The PDCCH may be transmitted in the DL control region, and the PDSCH maybe transmitted in the DL data region. The PUCCH may be transmitted inthe UL control region, and the PUSCH may be transmitted in the UL dataregion. Downlink control information (DCI), for example, DL datascheduling information, UL data scheduling information, and the like,may be transmitted on the PDCCH. Uplink control information (UCI), forexample, ACK/NACK information about DL data, channel state information(CSI), and a scheduling request (SR), may be transmitted on the PUCCH.The GP provides a time gap in the process of the UE switching from thetransmission mode to the reception mode or from the reception mode tothe transmission mode. Some symbols at the time of switching from DL toUL within a subframe may be configured as the GP.

FIG. 5 illustrates a synchronization signal block (SSB) structure. TheUE may perform cell search, system information acquisition, beamalignment for initial access, DL measurement, and so on based on an SSB.The term SSB is used interchangeably with synchronizationsignal/physical broadcast channel (SS/PBCH) block.

Referring to FIG. 5, an SSB is composed of a PSS, an SSS, and a PBCH.The SSB includes four consecutive OFDM symbols. The PSS, the PBCH, theSSS/PBCH, and the PBCH are transmitted on the respective OFDM symbols.Each of the PSS and the SSS includes one OFDM symbol and 127subcarriers, and the PBCH includes 3 OFDM symbols and 576 subcarriers.Polar coding and quadrature phase shift keying (QPSK) are applied to thePBCH. The PBCH includes data REs and demodulation reference signal(DMRS) REs in each OFDM symbol. There are three DMRS REs per RB, withthree data REs between every two adjacent DMRS REs.

Cell Search

The cell search refers to a procedure in which the UE obtainstime/frequency synchronization of a cell and detects a cell ID (e.g.,physical layer cell ID (PCID)) of the cell. The PSS may be used indetecting a cell ID within a cell ID group, and the SSS may be used indetecting a cell ID group. The PBCH may be used in detecting an SSB(time) index and a half-frame.

The cell search procedure of the UE may be summarized as described inTable 3 below.

TABLE 3 Type of Signals Operations 1^(st) step PSS * SS/PBCH block (SSB)symbol timing acquisition * Cell ID detection within a cell ID group (3hypothesis) 2^(nd) Step SSS * Cell ID group detection (336 hypothesis)3^(rd) Step PBCH * SSB index and Half frame (HF) index (Slot DMRS andframe boundary detection) 4^(th) Step PBCH * Time information (80 ms,System Frame Number (SFN), SSB index, HF) * Remaining Minimum SystemInformation (RMSI) Control resource set (CORESET)/ Search spaceconfiguration 5^(th) Step PDCCH and * Cell access information PDSCH *RACH configuration

FIG. 6 illustrates SSB transmission.

Referring to FIG. 6, an SSB is periodically transmitted according to theSSB periodicity. The basic SSB periodicity assumed by the UE in theinitial cell search is defined as 20 ms. After the cell access, the SSBperiodicity may be set to one of {5 ms, 10 ms, 20 ms, 40 ms, 80 ms, 160ms} by the network (e.g., the BS). An SSB burst set may be configured atthe beginning of an SSB period. The SSB burst set may be configured witha 5-ms time window (i.e., half-frame), and an SSB may be repeatedlytransmitted up to L times within the SS burst set. The maximum number oftransmissions of the SSB, L may be given according to the frequency bandof a carrier as follows. One slot includes up to two SSBs.

-   -   For frequency range up to 3 GHz, L=4    -   For frequency range from 3 GHz to 6 GHz, L=8    -   For frequency range from 6 GHz to 52.6 GHz, L=64

The time position of an SSB candidate in the SS burst set may be definedaccording to the SCS as follows. The time positions of SSB candidatesare indexed as (SSB indexes) 0 to L-1 in temporal order within the SSBburst set (i.e., half-frame).

-   -   Case A—15-kHz SCS: The indexes of the first symbols of candidate        SSBs are given as {2, 8}+14*n where n=0, 1 for a carrier        frequency equal to or lower than 3 GHz, and n=0, 1, 2, 3 for a        carrier frequency of 3 GHz to 6 GHz.    -   Case B—30-kHz SCS: The indexes of the first symbols of candidate        SSBs are given as {4, 8, 16, 20}+28*n where n =0 for a carrier        frequency equal to or lower than 3 GHz, and n=0, 1 for a carrier        frequency of 3 GHz to 6 GHz.    -   Case C—30-kHz SCS: The indexes of the first symbols of candidate        SSBs are given as {2, 8}+14*n where n=0, 1 for a carrier        frequency equal to or lower than 3 GHz, and n=0, 1, 2, 3 for a        carrier frequency of 3 GHz to 6 GHz.    -   Case D—120-kHz SCS: The indexes of the first symbols of        candidate SSBs are given as {4, 8, 16, 20}+28*n where n=0, 1, 2,        3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18 fora carrier        frequency above 6 GHz.    -   Case E—240-kHz SCS: The indexes of the first symbols of        candidate SSBs are given as {8, 12, 16, 20, 32, 36, 40, 44}+56*n        where n=0, 1, 2, 3, 5, 6, 7, 8 for a carrier frequency above 6        GHz.

FIG. 7 illustrates exemplary acquisition of information about DL timesynchronization at a UE.

Referring to FIG. 7, the UE may acquire DL synchronization by detectingan SSB. The UE may identify the structure of an SSB burst set based onthe index of the detected SSB, and thus detect a symbol/slot/half-frameboundary. The number of a frame/half-frame to which the detected SSBbelongs may be identified by SFN information and half-frame indicationinformation.

Specifically, the UE may acquire 10-bit SFN information, s0 to s9 from aPBCH. 6 bits of the 10-bit SFN information is acquired from a masterinformation block (MIB), and the remaining 4 bits is acquired from aPBCH transport block (TB).

Subsequently, the UE may acquire 1-bit half-frame indication informationc0. If a carrier frequency is 3GH or below, the half-frame indicationinformation may be signaled implicitly by a PBCH DMRS. The PBCH DMRSindicates 3-bit information by using one of 8 PBCH DMRS sequences.Therefore, if L=4, the remaining one bit except for two bits indicatingan SSB index in the 3-bit information which may be indicated by 8 PBCHDMRS sequences may be used for half-frame indication.

Finally, the UE may acquire an SSB index based on the DMRS sequence andthe PBCH payload. SSB candidates are indexed from 0 to L-1 in a timeorder within an SSB burst set (i.e., half-frame). If L=8 or 64, threeleast significant bits (LSBs) b0 to b2 of the SSB index may be indicatedby 8 different PBCH DMRS sequences. If L=64, three most significant bits(MSBs) b3 to b5 of the SSB index is indicated by the PBCH. If L=2, twoLSBs b0 and b1 of an SSB index may be indicated by 4 different PBCH DMRSsequences. If L=4, the remaining one bit b2 except for two bitsindicating an SSB index in 3-bit information which may be indicated by 8PBCH DMRS sequences may be used for half-frame indication.

System Information Acquisition

FIG. 8 illustrates a system information (SI) acquisition procedure. TheUE may obtain access stratum (AS)-/non-access stratum (NAS)-informationin the SI acquisition procedure. The SI acquisition procedure may beapplied to UEs in RRC_IDLE, RRC_INACTIVE, and RRC_CONNECTED states.

SI is divided into a master information block (MIB) and a plurality ofsystem information blocks (SIB s). The MIB and the plurality of SIBs arefurther divided into minimum SI and other SI. The minimum SI may includethe MIB and systemInformationBlock1 (SIB1), carrying basic informationrequired for initial access and information required to obtain the otherSI. SIB1 may also be referred to as remaining minimum system information(RMSI). For details, the following may be referred to.

-   -   The MIB includes information/parameters related to reception of        SIB1 and is transmitted on the PBCH of an SSB. The UE assumes        that a half-frame including an SSB is repeated every 20 ms        during initial cell selection. The UE may determine from the MIB        whether there is any control resource set (CORESET) for a        Type0-PDCCH common search space. The Type0-PDCCH common search        space is a kind of PDCCH search space and used to transmit a        PDCCH that schedules an SI message. In the presence of a        Type0-PDCCH common search space, the UE may determine (1) a        plurality of contiguous RBs and one or more consecutive symbols        included in a CORESET, and (ii) a PDCCH occasion (e.g., a        time-domain position at which a PDCCH is to be received), based        on information (e.g., pdcch-ConfigSIB1) included in the MIB. In        the absence of a Type0-PDCCH common search space,        pdcch-ConfigSIB1 provides information about a frequency position        at which the SSB/SIB1 exists and information about a frequency        range without any SSB/SIB1.    -   SIB1 includes information related to availability and scheduling        (e.g., a transmission periodicity and an SI-window size) of the        remaining SIBs (hereinafter, referred to as SIBx where x is an        integer equal to or larger than 2). For example, SIB1 may        indicate whether SIBx is broadcast periodically or in an        on-demand manner upon UE request. If SIBx is provided in the        on-demand manner, SIB1 may include information required for the        UE to transmit an SI request. A PDCCH that schedules SIB1 is        transmitted in the Type0-PDCCH common search space, and SIB1 is        transmitted on a PDSCH indicated by the PDCCH.    -   SIBx is included in an SI message and transmitted on a PDSCH.        Each SI message is transmitted within a periodic time window        (i.e., SI-window).

Beam Alignment

FIG. 9 illustrates exemplary multi-beam transmission of SSBs.

Beam sweeping refers to changing the beam (direction) of a wirelesssignal over time at a transmission reception point (TRP) (e.g., aBS/cell) (hereinafter, the terms beam and beam direction areinterchangeably used). Referring to FIG. 10, an SSB may be transmittedperiodically by beam sweeping. In this case, SSB indexes are implicitlylinked to SSB beams. An SSB beam may be changed on an SSB (index) basisor on an SS (index) group basis. In the latter, the same SSB beam ismaintained in an SSB (index) group. That is, the transmission beamdirection of an SSB is repeated for a plurality of successive SSBs. Themaximum allowed transmission number L of an SSB in an SSB burst set is4, 8 or 64 according to the frequency band of a carrier. Accordingly,the maximum number of SSB beams in the SSB burst set may be givenaccording to the frequency band of a carrier as follows.

-   -   For frequency range of up to 3 GHz, maximum number of beams=4    -   For frequency range from 3 GHz to 6 GHz, maximum number of        beams=8    -   For frequency range from 6 GHz to 52.6 GHz, maximum number of        beams=64

Without multi-beam transmission, the number of SSB beams is 1.

When the UE attempts initial access to the BS, the UE may align beamswith the BS based on an SSB. For example, the UE performs SSB detectionand then identifies a best SSB. Subsequently, the UE may transmit anRACH preamble in PRACH resources linked/corresponding to the index(i.e., beam) of the best SSB. The SSB may also be used for beamalignment between the BS and the UE even after the initial access.

Channel Estimation and Rate-Matching

FIG. 10 illustrates an exemplary method of indicating actuallytransmitted SSBs, SSB_tx.

Up to L SSBs may be transmitted in an SSB burst set, and the number andpositions of actually transmitted SSBs may be different for each BS orcell. The number and positions of actually transmitted SSBs are used forrate-matching and measurement, and information about actuallytransmitted SSBs is indicated as follows.

-   -   If the information is related to rate matching, the information        may be indicated by UE-specific RRC signaling or RMSI. The        UE-specific RRC signaling includes a full bitmap (e.g., of        length L) for frequency ranges below and above 6 GHz. The RMSI        includes a full bitmap for a frequency range below 6 GHz and a        compressed bitmap for a frequency range above 6 GHz, as        illustrated. Specifically, the information about actually        transmitted SSBs may be indicated by a group-bitmap (8 bits)+an        in-group bitmap (8 bits). Resources (e.g., REs) indicated by the        UE-specific RRC signaling or the RMSI may be reserved for SSB        transmission, and a PDSCH and/or a PUSCH may be rate-matched in        consideration of the SSB resources.    -   If the information is related to measurement, the network (e.g.,        BS) may indicate an SSB set to be measured within a measurement        period, when the UE is in RRC connected mode. The SSB set may be        indicated for each frequency layer. Without an indication of an        SSB set, a default SSB set is used. The default SSB set includes        all SSBs within the measurement period. An SSB set may be        indicated by a full bitmap (e.g., of length L) in RRC signaling.        When the UE is in RRC idle mode, the default SSB set is used.

In the NR system, a massive multiple input multiple output (MIMO)environment in which the number of transmission/reception (Tx/Rx)antennas is significantly increased may be under consideration. That is,as the massive MIMO environment is considered, the number of Tx/Rxantennas may be increased to a few tens or hundreds. The NR systemsupports communication in an above 6 GHz band, that is, a millimeterfrequency band. However, the millimeter frequency band is characterizedby the frequency property that a signal is very rapidly attenuatedaccording to a distance due to the use of too high a frequency band.Therefore, in an NR system operating at or above 6 GHz, beamforming (BF)is considered, in which a signal is transmitted with concentrated energyin a specific direction, not omni-directionally, to compensate for rapidpropagation attenuation. Accordingly, there is a need for hybrid BF withanalog BF and digital BF in combination according to a position to whicha BF weight vector/precoding vector is applied, for the purpose ofincreased performance, flexible resource allocation, and easiness offrequency-wise beam control in the massive MIMO environment.

Random Access Channel (RACH) Procedure

When a UE first accesses a BS or has no radio resource for signaltransmission, the UE may perform a RACH procedure to the BS.

The RACH procedure may be used for various purposes. For example, theRACH procedure may be used for initial network access from RRC_IDLE, anRRC connection re-establishment procedure, handover, UE-triggered ULdata transmission, transition from RRC_INACTIVE, time alignmentestablishment in SCell addition, other system information (OSI) requestand beam failure recovery, and so on. The UE may acquire ULsynchronization and UL transmission resources from the RACH procedure.

The RACH procedure may be divided into a contention-based RACH procedureand a contention-free RACH procedure. The contention-based RACHprocedure may be divided into a 4-step RACH procedure (4-step RACH) anda 2-step RACH procedure (2-step RACH).

(1) 4-Step RACH: Type-1 Random Access Procedure

FIG. 11 is a diagram illustrating an exemplary 4-step RACH procedure.

If the (contention-based) RACH procedure is performed in four steps(i.e., 4-step RACH procedure), the UE may transmit a message (message 1(Msg1)) including a preamble related to a specific sequence on aphysical random access channel (PRACH) (1101) and may receive a responsemessage (random access response (RAR) message) (message 2 (Msg2)) to thepreamble on a PDCCH and a PDSCH related thereto (1103). The UE maytransmit a message (message 3 (Msg3)) including a PUSCH based onscheduling information in the RAR (1105). The UE may perform acontention resolution procedure by receiving a PDCCH signal and a PDSCHsignal related thereto. To this end, the UE may receive a message(message 4 (Msg4)) containing contention resolution information on thecontention resolution procedure from the BS (1107).

The 4-step RACH procedure of the UE may be summarized as shown in Table4 below.

TABLE 4 Type of Signals Operations/Information obtained 1^(st) stepPRACH preamble in * Initial beam obtainment UL * Random selection ofRA-preamble ID 2^(nd) step * Random Access * Timing Advanced informationResponse on DL-SH * RA-preamble ID * Initial UL grant, Temporary C-RNTI3^(rd) step UL transmission on * RRC connection request UL-SCH * UEidentifier 4^(th) step Contention Resolution * Temporary C-RNTI on PDCCHfor on DL initial access * C-RNTI on PDCCH for UE in RRC CONNECTED

First, the UE may transmit a random access preamble over a PRACH in ULas Msg1 of the RACH procedure.

Random access preamble sequences of two different lengths are supported.Long sequence length 839 is applied with SCSs of 1.25 and 5 kHz, andshort sequence length 139 is applied with SCSs of 15, 30, 60 and 120kHz.

Multiple preamble formats are defined by one or more RACH OFDM symbolsand different cyclic prefixes (and/or guard times). The RACHconfiguration for the initial bandwidth of a primary cell (Pcell) may beincluded in system information of the cell and provided to the UE. TheRACH configuration includes information on the SCS of the PRACH,available preambles, preamble formats, and the like. The RACHconfiguration includes information on association between SSBs and RACH(time-frequency) resources. The UE transmits the random access preambleon a RACH time-frequency resource associated with a detected or selectedSSB.

The threshold of SSBs may be configured by the network for associationwith RACH resources. The RACH preamble may be transmitted orretransmitted based on SSB(s) having reference signal received power(RSRP) measured based thereon satisfying the threshold. For example, theUE may select one of the SSB(s) that satisfy the threshold and transmitor retransmit the RACH preamble based on a RACH resource associated withthe selected SSB. For example, upon retransmission of the RACH preamble,the UE may reselect one of the SSB(s) and retransmit the RACH preamblebased on a RACH resource associated with the reselected SSB. That is,the RACH resource for retransmission of the RACH preamble may be thesame as and/or different from the RACH resource for transmission of theRACH preamble.

When the BS receives a random access preamble from the UE, the BStransmits an RAR message (Msg2) to the UE. A PDCCH scheduling a PDSCHcarrying the RAR is cyclic redundancy check (CRC) scrambled with arandom access (RA) radio network temporary identifier (RNTI) (RA-RNTI)and then transmitted. Upon detecting the PDCCH CRC-scrambled with theRA-RNTI, the UE may receive the RAR from the PDSCH scheduled by DCIcarried on the PDCCH. The UE checks whether the RAR includes RARinformation in response to the preamble transmitted by the UE, i.e.,Msg1. The presence or absence of the RAR information in response to Msg1transmitted by the UE may be determined depending on whether there is arandom access preamble ID for the preamble transmitted by the UE. Ifthere is no response to Msg1, the UE may retransmit the RACH preamblewithin a predetermined number of times while performing power ramping.The UE may calculate PRACH transmission power for retransmitting thepreamble based on the most recent transmission power, power increment,and power ramping counter.

The RAR information may include a preamble sequence transmitted by theUE, a temporary cell-RNTI (TC-RNTI) allocated by the BS to the UE thathas attempted random access, and UL transmit time alignment information,UL transmission power adjustment information, and UL radio resourceallocation information. If the UE receives the RAR information foritself on the PDSCH, the UE may obtain timing advance information for ULsynchronization, an initial UL grant, a TC-RNTI. The timing advanceinformation may be used to control a UL signal transmission timing. Tobetter align PUSCH/PUCCH transmission by the UE with the subframe timingat the network, the network (e.g., BS) may obtain the timing advanceinformation based on timing information detected from a PRACH preamblereceived from the UE and transmit the timing advance information to theUE. The UE may transmit a UL signal over a UL shared channel based onthe RAR information as Msg3 of the RACH procedure. Msg3 may include anRRC connection request and a UE identifier. In response to Msg3, thenetwork may transmit Msg4, which may be treated as a contentionresolution message on DL. Upon receiving Msg4, the UE may enter theRRC_CONNECTED state.

As described above, a UL grant in the RAR may schedule PUSCHtransmission to the BS. A PUSCH carrying initial UL transmission basedon the UL grant in the RAR is also referred to as a Msg3 PUSCH. Thecontent of an RAR UL grant may start at the MSB and end at the LSB, andthe content may be given as shown in Table 5.

TABLE 5 Number RAR UL grant field of bits Frequency hopping flag 1 Msg3PUSH frequency resource 12 allocation Msg3 PUSCH time resourceallocation 4 Modulation and coding scheme (MCS) 4 Transmit power control(TPC) for 3 Msg3 PUSCH CSI request 1

A TPC command is used to determine the transmission power of the Msg3PUSCH. For example, the TPC command may be interpreted as shown in Table6.

TABLE 6 TPC command value [dB] 0 −6 1 −4 2 −2 3 0 4 2 5 4 6 6 7 8

(2) 2-Step RACH: Type-2 Random Access Procedure

FIG. 12 is a diagram illustrating an exemplary 2-step RACH procedure.

The 2-step RACH procedure in which the (contention-based) RACH procedureis performed in two steps has been proposed to simplify the RACHprocedure, that is, to achieve low signaling overhead and low latency.

The operations of transmitting Msg1 and Msg3 in the 4-step RACHprocedure may be performed as one operation in the 2-step RACH procedurewhere the UE transmits one message (message A (MsgA)) including a PRACHand a PUSCH. The operations in which the BS transmits Msg2 and Msg4 inthe 4-step RACH procedure may be performed as one operation in the2-step RACH procedure where the BS transmits one message (message B(MsgB)) including an RAR and contention resolution information.

That is, in the 2-step RACH procedure, the UE may combine Msg1 and Msg3of the 4-step RACH procedure into one message (e.g., MsgA) and transmitthe one message to the BS (1201).

In addition, in the 2-step RACH procedure, the BS may combine Msg2 andMsg4 of the 4-step RACH procedure into one message (e.g., MsgB) andtransmit the one message to the UE (S1203).

Based on the combination of these messages, the 2-step RACH proceduremay provide a low-latency RACH procedure.

Specifically, MsgA of the 2-step RACH procedure may include a PRACHpreamble contained in Msg1 and data contained in Msg3. MsgB of the2-step RACH procedure may include an RAR contained in Msg2 andcontention resolution information contained in Msg4.

(3) Contention-Free RACH

FIG. 13 is a diagram illustrating an exemplary contention-free RACHprocedure.

The contention-free RACH procedure may be used when the UE is handedover to another cell or BS or when requested by a command from the BS.The basic steps of the contention-free RACH procedure are similar tothose of the contention-based RACH procedure. However, in thecontention-free RACH procedure, the BS allocates a preamble to be usedby the UE (hereinafter, dedicated random access preamble) to the UE(1301), unlike the contention-based RACH procedure in which the UEarbitrarily selects a preamble to be used from among a plurality ofrandom access preambles. Information on the dedicated random accesspreamble may be included in an RRC message (e.g., handover command) orprovided to the UE through a PDCCH order. When the RACH procedure isinitiated, the UE transmits the dedicated random access preamble to theBS (1303). When the UE receives an RAR from the BS, the RACH procedureis completed (1305).

In the contention-free RACH procedure, a CSI request field in an RAR ULgrant indicates whether the UE includes an aperiodic CSI report incorresponding PUSCH transmission. The SCS for Msg3 PUSCH transmission isprovided by an RRC parameter. The UE may transmit a PRACH and a Msg3PUSCH on the same UL carrier of the same serving cell. The UL BWP forMsg3 PUSCH transmission is indicated by system information block 1(SIB1).

(4) Mapping Between SSBs and PRACH Resources (Occasions)

FIGS. 14 and 15 are diagrams illustrating transmission of SSBs and PRACHresources linked to the SSBs according to various embodiments of thepresent disclosure.

To communicate with one UE, the BS may need to find out what is theoptimal beam direction between the BS and UE. Since it is expected thatthe optimal beam direction will vary according to the movement of theUE, the BS needs to continuously track the optimal beam direction. Aprocess of finding out the optimal beam direction between the BS and UEis called a beam acquisition process, and a process of continuouslytracking the optimal beam direction between the BS and UE is called abeam tracking process. The beam acquisition process may be required inthe following cases: 1) initial access where the UE attempts to accessthe BS for the first time; 2) handover where the UE is handed over fromone BS to another BS; and 3) beam recovery for recovering beam failure.The beam failure means a state in which while performing the beamtracking to find out the optimal beam between the UE and BS, the UEloses the optimal beam and thus is incapable of maintaining the optimalcommunication state with the BS or incapable of communicating with theBS.

In the NR system, a multi-stage beam acquisition process is beingdiscussed for beam acquisition in an environment using multiple beams.In the multi-stage beam acquisition process, the BS and UE perform aconnection setup by using a wide beam in the initial access stage. Afterthe connection setup is completed, the BS and UE perform the highestquality of communication by using a narrow beam. The beam acquisitionprocess in the NR system applicable to various embodiments of thepresent disclosure may be performed as follows.

-   -   1) The BS transmits a synchronization block for each wide beam        to allow the UE to discover the BS in the initial access stage,        that is, in order for the UE to find the optimal wide beam to be        used in the first stage of the beam acquisition by performing        cell search or cell acquisition and measuring the channel        quality of each wide beam.    -   2) The UE performs the cell search on the synchronization block        for each beam and acquires a DL beam based on the detection        result for each beam.    -   3) The UE performs a RACH procedure to inform the BS that the UE        discovers that the UE intends to access the BS.    -   4) The BS connects or associates the synchronization block        transmitted for each beam with a PRACH resource to be used for        PRACH transmission to allow the UE to simultaneously inform the        RACH procedure and the DL beam acquisition result (e.g., beam        index) at wide beam levels. If the UE performs the RACH        procedure on a PRACH resource associated with the optimal beam        direction that the UE finds, the BS obtains information on the        DL beam suitable for the UE by receiving a PRACH preamble.

In the multi-beam environment, it is a problem whether the UE and/or TRPis capable of accurately determining the directions of a transmission(TX) and/or reception (RX) beam between the UE and TRP. In themulti-beam environment, repetition of signal transmission or beamsweeping for signal reception may be considered based on the TX/RXreciprocal capability of the TRP (e.g., BS) or UE. The TX/RX reciprocalcapability of the TRP and UE is also referred to as TX/RX beamcorrespondence of the TRP and UE. In the multi-beam environment, if theTX/RX reciprocal capability of the TRP and UE is not valid (that is, notheld), the UE may not be capable of transmitting a UL signal in the beamdirection in which the UE receives a DL signals. This is because the ULoptimal path may be different from the DL optimal path. The TX/RX beamcorrespondence of the TRP may be valid (held) if the TRP is capable ofdetermining a TRP RX beam for UL reception based on DL measurementsmeasured by the UE for one or more TX beams of the TRP and/or if the TRPis capable of determining a TRP TX beam for DL transmission based on ULmeasurements measured by the TRP for one or more RX beams of the TRP.The TX/RX beam correspondence of the UE may be valid (held) if the UE iscapable of determining a UE RX beam for UL transmission based on DLmeasurements measured by the UE for one or more RX beams of the UEand/or if the UE is capable of determining a UE TX beam for DL receptionbased on an indication from the TRP, which is related to UL measurementsfor one or more TX beams of the UE.

(5) PRACH Preamble Structure

In the NR system, a RACH signal used for initial access to the BS, thatis, initial access to the BS through a cell used by the BS may beconfigured based on the following elements.

-   -   Cyclic prefix (CP): The CP serves to prevent interference from        previous (OFDM) symbols and bundle PRACH preamble signals        arriving at the BS with various time delays in one same time        zone. That is, if the CP is configured to match the maximum        radius of a cell, PRACH preambles transmitted by UEs in the cell        on the same resource may be within a PRACH reception window        having a PRACH preamble length configured by the BS for PRACH        reception. The length of the CP is generally set greater than or        equal to the maximum round trip delay. The CP may have a length        of TCP.    -   Preamble (sequence): A sequence may be defined for the BS to        detect signal transmission, and the preamble serves to carry        this sequence. The preamble sequence may have a length of TSEQ.    -   Guard time (GT): The GT is a time duration defined to prevent a        PRACH signal that is transmitted from the point farthest from        the BS in PRACH coverage and received by the BS with a delay        from interfering with a signal that is received after a PRACH        symbol duration. Since the UE transmits no signal in the GT        period, the GT may not be defined as a PRACH signal. The GT may        have a length of TGP.

(6) Mapping to Physical Resources for Physical Random-Access Channel

Random access preambles may be transmitted only on time resourcesobtained based on predetermined tables (RACH configuration tables) forRACH configurations, frequency range 1 (FR1), frequency range 2 (FR2),and predetermined spectrum types.

The PRACH configuration index in RACH configuration tables may be givenas follows.

-   -   For a RACH configuration table for random access configurations        for FR1 and unpaired spectrum, the PRACH configuration index may        be given by a higher layer parameter prach-ConfigurationIndexNew        (if configured). Otherwise, the PRACH configuration index may be        given by prach-ConfigurationIndex,        msgA-prach-ConfigurationIndex, or        msgA-prach-ConfigurationIndexNew (if configured).    -   For a RACH configuration table for random access configurations        for FR1 and paired spectrum/supplementary uplink and a RACH        configuration table for random access configurations for FR2 and        unpaired spectrum, the PRACH configuration index may be given by        a higher layer parameter prach-ConfigurationIndex or        msgA-prach-ConfigurationIndexNew (if configured).

For each case, the RACH configuration table may show relationshipsbetween one or more of the following parameters: PRACH configurationindex, preamble format, n_(SFN) mod x=y, subframe number, startingsymbol, number of PRACH slots, number of time-domain PRACH occasionswithin a PRACH slot, and PRACH duration.

Each case may be:

-   -   (1) Random access configurations for FR1 and paired        spectrum/supplementary uplink;    -   (2) Random access configurations for FR1 and unpaired spectrum;        or    -   (3) Random access configurations for FR2 and unpaired spectrum.

Table 7 below shows a part of the RACH configuration table for (2)random access configurations for FR1 and unpaired spectrum.

TABLE 7 N_(t) ^(RAslot), number of time- Number domain of PRACH PRACHoccasions PRACH n_(SFN) slots within a N_(dur) ^(RA), ConfigurationPreamble modx = y Subframe Starting within a PRACH PRACH Index format xy number symbol subframe slot duration 0 0 16 1 9 0 — — 0 1 0 8 1 9 0 —— 0 2 0 4 1 9 0 — — 0 3 0 2 0 9 0 — — 0 4 0 2 1 9 0 — — 0 5 0 2 0 4 0 —— 0 6 0 2 1 4 0 — — 0 7 0 1 0 9 0 — — 0 8 0 1 0 8 0 — — 0 9 0 1 0 7 0 —— 0

The RACH configuration table shows specific values for parameters (e.g.,preamble format, periodicity, SFN offset, RACH subframe/slot index,starting OFDM symbol, number of RACH slots, number of occasions, OFDMsymbols for RACH format, etc.) required to configure RACH occasions.When the RACH configuration index is indicated, specific values relatedto the indicated index may be used.

For example, when the starting OFDM symbol parameter is n, one or moreconsecutive (time-domain) RACH occasions may be configured from an OFDMsymbol having index #n.

For example, the number of one or more RACH occasions may be indicatedby the following parameter: number of time-domain PRACH occasions withina RACH slot.

For example, a RACH slot may include one or more RACH occasions.

For example, the number of RACH slots (in a subframe and/or slot with aspecific SCS) may be indicated by the parameter: number of RACH slots.

For example, a system frame number (SFN) including RACH occasions may bedetermined by n_(SFN) mod x=y, where mod is a modular operation (moduloarithmetic or modulo operation) which is an operation to obtainremainder r obtained by dividing dividend q by divisor d (r=q mod (d)).

For example, a subframe/slot (index) including RACH occasions in asystem frame may be indicated by the parameter: RACH subframe/slotindex.

For example, a preamble format for RACH transmission/reception may beindicated by the parameter: preamble format.

Referring to FIG. 16(a), for example, when the starting OFDM symbol isindicated as 0, one or more consecutive (time-domain) RACH occasions maybe configured from OFDM symbol #0. For example, the number of one ormore RACH occasions may depend on a value indicated by the parameter:number of time-domain RACH occasions within a RACH slot. For example,the preamble format may be indicated by the parameter: preamble format.For example, preamble formats A1, A2, A3, B4, C0, C2, etc. may beindicated. For example, one of the last two OFDM symbols may be used asthe GT, and the other may be used for transmission of other UL signalssuch as a PUCCH, a sounding reference signal (SRS), etc.

Referring to FIG. 16(b), for example, when the starting OFDM symbol isindicated by 2, one or more consecutive (time-domain) RACH occasions maybe configured from OFDM symbol #2. For example, 12 OFDM symbols may beused for a RACH occasion, and no GT may be configured in the last OFDMsymbol. For example, the number of one or more RACH occasions may dependon a value indicated by the parameter: number of time-domain RACHoccasions within a RACH slot. For example, the preamble format may beindicated by the parameter: preamble format. For example, preambleformats A1/B1, B1, A2/B2, A3/B3, B4, C0, C2, etc. may be indicated.

Referring to FIG. 16(c), for example, when the starting OFDM symbol isindicated as 7, one or more consecutive (time-domain) RACH occasions maybe configured from OFDM symbol #7. For example, 6 OFDM symbols may beused for an RACH occasion, and the last OFDM symbol (OFDM symbol #13)may be used for transmission of other UL signals such as a PUCCH, anSRS, etc. For example, the number of one or more RACH occasions maydepend on a value indicated by the parameter: number of time-domain RACHoccasions within a RACH slot. For example, the preamble format may beindicated by the parameter: preamble format. For example, preambleformats A1, B1, A2, A3, B3, B4, C0, C2, etc. may be indicated.

For example, the parameters included in the RACH configuration table maysatisfy predetermined correspondence relationships identified/determinedby the RACH configuration table and the RACH configuration index. Forexample, the predetermined correspondence relationships may be satisfiedbetween the following parameters: PRACH configuration index, RACHformat, period (x)=8, SFN offset (y), subframe number, starting symbol(index), number of PRACH slots within a subframe, number of PRACHoccasions within a PRACH slot, PRACH duration/OFDM symbols for RACHformat, etc. The correspondence relationships may be identified by theRACH configuration index and the RACH configuration table.

Hereinafter, methods for performing the RACH procedure according toembodiments of the present disclosure will be described.

With reference to FIGS. 17 to 19, overall operation processes of the UEand BS according to embodiments of the present disclosure will bedescribed.

FIG. 17 illustrates the overall operation process of the UE according toan embodiment of the present disclosure.

Referring to FIG. 17, the UE may transmit MsgA to the BS (S1701). Inthis case, MsgA may include only a PRACH or may include a PUSCH as wellas the PRACH. When MsgA includes both the PRACH and PUSCH, the UE maytransmit the PUSCH after transmitting the PRACH.

In this case, the UE may transmit the PRACH while knowing an SFN fortransmitting the PRACH. Alternatively, the UE may transmit the PRACHwithout knowing the SFN for transmitting the PRACH. Details thereof willbe described in the following embodiments.

The UE may monitor and receive DCI scheduling MsgB (S1703). The UE maydescramble a CRC from the DCI based on a MsgB-RNTI. If the UE confirmsthe CRC, the UE may decode information bits included in the DCI.

The UE may decode lower two bits for the index of an SFN in the DCI andthen compare the lower two bits with lower two bits for the index of theSFN for transmitting the PRACH.

However, if the UE transmits the PRACH without knowing the SFN fortransmitting the PRACH, the UE may not compare the lower two bits forthe SFN included in the DCI and the lower two bits for the SFN fortransmitting the PRACH. For example, in general, when the UE performshandover, the UE may need to perform a PBCH decoding process to obtainthe SFN of a target cell to be handed over. However, the RACH proceduremay be performed with no PBCH decoding to reduce the time delay due tothe PBCH decoding and a burden on the UE due to the PBCH decoding. Inthis case, when the UE intends to the PRACH to the target cell, the UEmay transmit the PRACH without knowing the SFN for the PRACHtransmission.

This will be described in detail in the following embodiments.

The UE may receive a PDSCH for an RAR based on the DCI (S1705). In thiscase, the UE may receive the PDSCH according to the result of comparingthe lower two bits for the SFN included in the DCI and the lower twobits for the SFN for transmitting the PRACH. On the other hand, the UEmay receive the PDSCH regardless of the result of comparing the lowertwo bits for the SFN included in the DCI and the lower two bits for theSFN for transmitting the PRACH.

In addition, the UE may receive the PDSCH or perform other operationsinstead of receiving the PDSCH, depending on whether the UE is capableof comparing the lower two bits for the SFN included in DCI and thelower two bits for the SFN for transmitting the PRACH and/or accordingto the comparison result.

The UE operations depending on whether the UE is capable of comparingthe lower two bits for the SFN included in the DCI and the lower twobits for the SFN for transmitting the PRACH and/or according to thecomparison result may be based on the following embodiments.

The UE may transmit a UL signal based on the PDSCH (S1707). In thiscase, the UL signal transmitted by the UE may vary depending on the RARof the PDSCH and depending on whether the PDSCH is received. Forexample, if the RAR is a fallback RAR, the UE may transmit the PRACH forthe Type-1 RACH procedure. As another example, if the RAR is a successRAR, the UE may transmit a PUCCH by including HARQ-ACK informationcorresponding to an ACK in the PUCCH.

If the UE does not receive the PDSCH, the UE may transmit the PRACHaccording to the Type-1 RACH procedure or transmit (or retransmit) thePRACH and PUSCH according to the Type-2 RACH procedure.

The above-described UE operations according to S1701 to S1707 may bebased on one or more of the following embodiments. That is, the UEoperations according to S1701 to S1707 may be performed based on any oneof the following embodiments or any combination of two or more of thefollowing embodiments.

FIG. 18 is a diagram for explaining the overall operation process of theBS according to an embodiment of the present disclosure.

Referring to FIG. 18, the BS may receive MsgA from the UE (S1801). Inthis case, MsgA may include only a PRACH or may include a PUSCH as wellas the PRACH. When MsgA includes both the PRACH and PUSCH, the BS mayreceive the PUSCH after receiving the PRACH.

The BS may decode MsgA and transmit DCI having a CRC scrambled by aMsgB-RNTI to the UE based on the decoding result (S1803).

The BS may transmit a PDSCH for an RAR based on the DCI (S1805). If theBS detects both the PRACH and PUSCH in S1801, the RAR may be a successRAR. If the BS detects only the PRACH and does not detect the PUSCH inS1801, the RAR may be a fallback RAR. If the BS does not detect both thePRACH and PUSCH in S1801, the BS may not transmit both the DCI andPDSCH. That is, in this case, S1803 and S1805 may be omitted.

If the BS transmits the PDSCH, the BS may receive a UL signal based onthe PDSCH (S1807). In this case, the UL signal may vary depending on theRAR of the PDSCH and depending on whether the UE receives the PDSCH. Forexample, if the RAR is the fallback RAR, the BS may receive the PRACHfor the Type-1 RACH procedure. As another example, if the RAR is thesuccess RAR, the BS may receive a PUCCH including HARQ-ACK informationcorresponding to an ACK.

If the UE does not receive the PDSCH, the BS may receive the PRACHaccording to the Type-1 RACH procedure or receive (or receive again) thePRACH and PUSCH according to the Type-2 RACH procedure.

The above-described BS operations according to S1801 to S1807 may bebased on one or more of the following embodiments. That is, the BSoperations according to S1801 to S1807 may be performed based on any oneof the following embodiments or any combination of two or more of thefollowing embodiments.

FIG. 19 is a diagram for explaining an overall operation process of anetwork according to an embodiment of the present disclosure.

Referring to FIG. 19, the UE may transmit MsgA to the BS (S1901). Inthis case, MsgA may include only a PRACH or may include a PUSCH as wellas the PRACH. When MsgA includes both the PRACH and PUSCH, the UE maytransmit the PUSCH after transmitting the PRACH.

In this case, the UE may transmit the PRACH while knowing an SFN fortransmitting the PRACH. Alternatively, the UE may transmit the PRACHwithout knowing the SFN for transmitting the PRACH. Details thereof willbe described in the following embodiments.

The BS may decode received MsgA (S1903) and transmit DCI having a CRCscrambled by a MsgB-RNTI to the UE based on the decoding result (S1905).

The UE may monitor and receive the DCI scheduling MsgB (S1703). The UEmay descramble the CRC from the DCI based on the MsgB-RNTI. If the UEconfirms the CRC, the UE may decode information bits included in theDCI.

The UE may decode lower two bits for the index of an SFN in the DCI andthen compare the lower two bits with lower two bits for the index of theSFN for transmitting the PRACH.

However, if the UE transmits the PRACH without knowing the SFN fortransmitting the PRACH, the UE may not compare the lower two bits forthe SFN included in the DCI and the lower two bits for the SFN fortransmitting the PRACH. For example, in general, when the UE performshandover, the UE may need to perform PBCH decoding to obtain the SFN ofa target cell to be handed over. However, the RACH procedure may beperformed with no PBCH decoding to reduce the time delay caused by thePBCH decoding and a burden on the UE due to the PBCH decoding. In thiscase, when the UE intends to transmit the PRACH to the target cell, theUE may transmit the PRACH without knowing the SFN for the PRACHtransmission.

This will be described in detail in the following embodiments.

The BS may transmit a PDSCH for an RAR based on the DCI (S1907). If theBS detects both the PRACH and PUSCH in S1903, the RAR may be a successRAR. If the BS detects only the PRACH and does not detect the PUSCH inS1903, the RAR may be a fallback RAR. If the BS does not detect both thePRACH and PUSCH in S1903, the BS may not transmit the DCI and PDSCH.That is, in this case, S1905 and S1907 may be omitted. In this case, theUE may transmit (or retransmit) MsgA to the BS.

The UE may receive the PDSCH according to the result of comparing thelower two bits for the SFN included in the DCI and the lower two bitsfor the SFN for transmitting the PRACH. On the other hand, the UE mayreceive the PDSCH regardless of the result of comparing the lower twobits for the SFN included in the DCI and the lower two bits for the SFNfor transmitting the PRACH.

In addition, the UE may receive the PDSCH or perform other operationswithout receiving the PDSCH, depending on whether the UE is capable ofcomparing the lower two bits for the SFN included in DCI and the lowertwo bits for the SFN for transmitting the PRACH and/or according to thecomparison result.

The UE operations depending on whether the UE is capable of comparingthe lower two bits for the SFN included in the DCI and the lower twobits for the SFN for transmitting the PRACH and/or according to thecomparison result may be based on the following embodiments.

The UE may transmit a UL signal based on the PDSCH (S1909). In thiscase, the UL signal transmitted by the UE may vary depending on the RARof the PDSCH and depending on whether the PDSCH is received. Forexample, if the RAR is the fallback RAR, the BS may transmit the PRACHfor the Type-1 RACH procedure. As another example, if the RAR is thesuccess RAR, the BS may transmit a PUCCH by including HARQ-ACKinformation corresponding to an ACK in the PUCCH.

If the UE does not receive the PDSCH, the UE may transmit the PRACHaccording to the Type-1 RACH procedure or transmit (or retransmit) thePRACH and PUSCH according to the Type-2 RACH procedure.

The above-described UE operations according to S1901 to S1909 may bebased on one or more of the following embodiments. That is, the UEoperations according to S1901 to S1909 may be performed based on any oneof the following embodiments or any combination of two or more of thefollowing embodiments.

Hereinafter, particular embodiments of the present disclosure will bedescribed based on FIGS. 17 to 19.

1. Embodiment 1

In the 2-step RACH procedure, the following three cases may beconsidered for network operations depending on whether the BSsuccessfully receives MsgA.

-   -   Case 1: When the BS successfully detects both a PRACH preamble        and a PUSCH, the BS may transmit MsgB to the UE.    -   Case 2: When the BS detects only a PRACH preamble and fails to        detect a PUSCH, the BS may transmit a fallback RAR instructing        the UE to perform the 4-step RACH procedure.

The BS may include a message instructing Msg3 transmission of the 4-stepRACH procedure in MsgB to transmit the message to the UE. The UE maymonitor a PDCCH for MsgB and receive the PDCCH related to MsgB. Inaddition, the UE may decode a PDSCH related to the PDCCH and then obtainan indicator for UE operations.

For example, when the UE receives Msg3 of the 4-step RACH procedure, theUE may transmit a PUSCH after a predetermined time.

-   -   Case 3: When the BS fails to detect a PRACH preamble, the BS may        not transmit an RAR or MsgB to the UE. The UE may transmit (or        retransmit) MsgA if the UE fails to receive the RAR or MsgB for        a predetermined period of time (e.g., monitoring window for MsgB        reception). On the other hand, when the BS fails to detect the        PRACH preamble, the BS may attempt to detect a PUSCH. However,        the BS may not attempt to detect the PUSCH.

Meanwhile, in Case 1 and/or Case 2, an RNTI (e.g., TC-RNTI) may berequired to monitor the PDCCH for MsgB. However, it may be difficult toallocate a TC-RNTI to the UE that intends to perform PDCCH monitoring.Therefore, it is necessary to study whether TC-RNTI based PDCCHmonitoring is required. If necessary, a method for allocating a TC-RNTIneeds to be studied. In addition, it is also necessary to study whethera TC-RNTI is commonly used for a group of UEs or is allocated to eachUE.

To this end, an RNTI used by the UE to monitor the PDCCH for MsgB may bedefined. Such an RNTI may be provided in the RAR. When the UE transmitsa PRACH preamble and the BS detects the PRACH preamble, the BS maytransmit to the UE a response (e.g., RAR) for a random access procedureidentity (RAPID) related to the detected PRACH preamble. In this case,the BS may include information on the RNTI related to the RAPID in theRAR to transmit the information on the RNTI to the UE. If the UE checksthe RAPID, which was transmitted by the UE, from the RAR and also checksthe RNTI related to the RAPID, the UE may transmit UL data such as aPUSCH based on the TC-RNTI or may monitor the PDCCH for MsgB or a PDCCHfor other DL data (e.g., PDSCH). In addition, the UE may use thecorresponding RNTI as the initialization seed value of a scramblingsequence for UL data.

To generate the RNTI for monitoring the PDCCH for MsgB, Equation 1,which is used to generate an RA-RNTI related to a specific RACH occasion(RO), may be used.RA_RNTI=1+s_id+14*t_id+14*80*f_id+14*80*8*ul_carrier_id   [Equation 1]

In Equation 1, s_id denotes the first OFDM symbol index of a transmittedPRACH and has a value of 0≤s≤_id<14.

In Equation 1, t_id denotes the first slot index in a system frame ofthe transmitted PRACH and has a value of 0≤t_id<80.

In Equation 1, f_id denotes the index of the PRACH in the frequencydomain and has a value of 0≤f_id<8.

In Equation 1, ul_carrier_id denotes the indicator for a UL carrier.Specifically, ul_carrier_id has a value of ‘0’ if the UL carrier is anormal carrier and has a value of ‘1’ if the UL carrier is asupplemental uplink (SUL) carrier.

According to embodiments of the present disclosure, when a 2-step PRACHpreamble is transmitted on an RO, a TC-RNTI related to the correspondingRO or a new RNTI may be defined. As a parameter for this, an RNTI may begenerated by applying a predetermined offset to a parameter related to atime resource to which the RO is mapped. For example, there are actuallyunused indices and used indices among indices for s_id and/or t_id ofEquation 1. Accordingly, indices other than those used for s_id and/ort_id where the corresponding RO is mapped may be used.

For example, if an RA-RNTI of the 4-step RACH procedure is generatedbased on a slot index and an OFDM symbol starting position (or startingOFDM symbol index) included in a RACH configuration table, an RNTI ofthe 2-step RACH procedure may be generated by applying a predeterminedoffset to the slot index and the OFDM symbol starting position (orstarting OFDM symbol index) included in the RACH configuration table.

For example, a PRACH preamble based on a short sequence may consist ofat least two OFDM symbols. For PRACH preamble format A1, OFDM symbolindex 0, 2, 4, 6, 8 or 10 may be used for the RA-RNTI of the 4-step RACHprocedure, and OFDM symbol index 1, 3, 5, 7, 9 or 11 may not be used.Accordingly, OFDM symbol index 1, 3, 5, 7, 9 or 11 may be used togenerate the RNTI of the 2-step RACH procedure.

Meanwhile, a slot index may be used to generate the RNTI of the 2-stepRACH procedure. Even if the RACH configuration duration is 10 ms forboth the 2-step RACH and 4-step RACH procedures, for the RA-RNTI of the4-step RACH procedure, only slot index 0, 2, 4, 6 or 8 are used atintervals of 2 ms based on 15 kHz slots. Therefore, slot index 1, 3, 5,7 or 9 may be used for the RNTI of the 2-step RACH procedure.

That is, the RNTI of the 2-step RACH procedure may be generated byselecting a value not used for generating the RNTI of the 4-step RACHprocedure from at least one of s_id and t_id. In this case, consideringLid, at least 8 different RNTIs may be generated.

As another example, if the transmission times of the 2-step PRACHpreamble and the 4-step PRACH preamble are divided in units ofsubframes, more RNTIs may be generated for 2-step RACH procedure. Forexample, if a duration of 20 ms is used for the RACH configuration, thefirst half of 10 ms may be used for the 4-step RACH procedure (or 2-stepRACH procedure), and the latter half of 10 ms may be used for the 2-stepRACH procedure (or 4-step RACH procedure).

On the other hand, when the 2-step RACH procedure and the 4-step RACHprocedure share the same RO, a slot index indicated by the RACHconfiguration may be used to generate the RA-RNTI of the 4-step RACHprocedure, and a specific offset may be applied to the slot indexindicated by the RACH configuration to generate the 2-step RACH RNTI.

For example, assuming that slot indices 0 to 79 are supported for theRACH generation, if the SCS is 15 kHz or 30 kHz in FR1, slot indices 0to 39 may be used for the 4-step RACH procedure, and slot indices 40 to79 may be used for the 2-step RACH procedure.

If it is indicated that the RACH slot index for the 4-step RACHprocedure is 0, 2, 4, 6 or 8, slot index 1, 3, 5, 7 or 9 may be used togenerate the RNTI of the 2-step RACH procedure.

In addition, slot indices 0 to 9 may be used for the RACH slot with anSCS of 15 kHz, and slot indices 0 to 39 may be used for the RACH slotwith an SCS of 60 kHz. In this case, if an SCS of 30/120 kHz isindicated, only one of two slots included in the 15/60 kHz SCS slots maybe used to generate the RA-RNTI of the 4-step RACH procedure. In thiscase, the remaining one slot index may be used to generate the RNTI ofthe 2-step RACH procedure.

As another example, the 2-step RNTI and the 4-step RA-RNTI may begenerated with different values as follows: a slot index and/or OFDMsymbol index for generating the RA-RNTI of the 4-step RACH procedure maybe maintained for a specific time duration, and a different slot indexand/or OFDM symbol index may be used for the RA-RNTI of the 2-step RACHprocedure. Here, the time duration used for generating the 2-step RNTIprocedure may be after the time duration for generating the RA-RNTI ofthe 4-step RACH procedure.

On the other hand, if the maximum length of an RAR window is 10 ms, acontention resolution timer for receiving Msg4 may be configured tooperate for a time duration longer than 10 ms. For example, referring toFIG. 20, when the length of the RAR window is 10 ms, the contentionresolution timer may have a length of 20 ms including two RAR windows.In this case, if a TC-RNTI related to an RO or a new RNTI is created,the TC-RNTI or the new RNTI may overlap every 10 ms. In order to solvethis problem, a time offset value applied to the RO may vary every 10ms.

As another example, the UE may generate an RA-RNTI based on an RO at thetime of transmitting a PRACH preamble. Thereafter, the UE may monitor aPDCCH based on the corresponding RA-RNTI. In this case, the PDCCH to bemonitored may be for an RAR or MsgB.

As another example, the UE may recalculate the RA-RNTI for monitoringthe PDCCH related to the RO after a lapse of a predetermined time (e.g.,10 ms) from the time at which the UE monitored the PDCCH. To generatingan RA-RNTI different from the previous RA-RNTI, the above-describedmethod using slot indices or OFDM symbol indices may be considered.

On the other hand, the above-described method is not limitedly appliedto PDCCH monitoring of the 2-step RACH procedure. That is, the methodmay be applied even when a time duration (e.g., monitoring window) forPDCCH monitoring of the 4-step RACH procedure becomes longer than apredetermined level. For example, considering that PDCCH transmissionmay be delayed due to Listen-Before-Talk (LBT) in unlicensed bands, theabove-described method may be considered when the RAR monitoring windowof the 4-step RACH procedure increases to 10 ms or more.

As another example, the UE may initially generate an RA-RNTI bysubstituting slot indices on an RO with slot indices in a time durationof 20 ms or more. For example, for the 15 kHz SCS, the UE may substituteslots included in two frames with slot indices 0 to 19 and use the slotindices to generate the RA-RNTI. To this end, the UE needs to knowexactly the starting and ending points of the time duration of 20 ms ormore. However, when the UE performs handover in an asynchronous network,the UE needs to obtain SFN information on a target cell in order tosecure the boundary of a time duration longer than the 10 ms duration ofthe target cell. Since the corresponding information is included in aPBCH, the UE needs to decode the PBCH to obtain the SFN information onthe target cell. Therefore, to implement this embodiment, thepossibility that latency may occur due to PBDH decoding during handoveralso needs to be considered.

The 2-step RACH procedure and the 4-step RACH procedure may share thesame RO. In this case, a UE performing the 2-step RACH procedure and aUE performing the 4-step RACH procedure may each monitor an RAR. AnRA-RNTI used for RAR monitoring may be determined according to the RO.In addition, the UE performing the 2-step RACH procedure needs tomonitor MsgB. However, an RNTI for monitoring MsgB needs to be differentfrom the RNTI for the RAR. For the RNTI for MsgB monitoring, theexisting RA-RNTI generation equation may be reused. For example, theRNTI for MsgB may be generated by the above-described embodimentsincluding the embodiment based on Equation 1.

In the following, the RNTI generation method described in the examplesof Embodiment 1 and examples to which the RNTI generation method areapplicable will be summarized.

(1) Usage 1: The RNTI generation method may be used to distinguish theRA-RNTI of the 2-step RACH procedure and the RA-RNTI of the 4-step RACHprocedure.

(2) Usage 2: In the 2-step RACH procedure, both an RAR and MsgB needs tobe monitored. Accordingly, Embodiment 1 may be used to distinguish anRA-RNTI for RAR monitoring and an RNTI for msgB monitoring.

(3) Usage 3: When the length of a PDCCH monitoring window exceeds 10 ms,the RNTI generation method may be used to distinguish an RA-RNTI usedfor RAR monitoring on an RO at a specific time point and an RA-RNTI usedfor RAR monitoring on an RO having the same OFDM symbol, slot, andfrequency position as the RO at the specific time point but having anoffset of 10 ms.

Usage 3 may be applied to the following scenarios.

1) For transmission in an unlicensed band, it may be difficult to obtainan occasion to transmit a PDCCH due to the LBT, and thus the length of aPDCCH monitoring window may be configured to exceed 10 ms. For example,the length of the PDCCH monitoring window may be set to 20 ms, 30 ms, or40 ms.

2) The size of a MsgB monitoring window of the 2-step RACH procedure mayexceed 10 ms.

3) If RA-RNTIs for MsgB monitoring in the 2-step RACH procedure aregenerated in groups of PUSCH occasions to which a specific RO is mapped(e.g., UL time and frequency resources for MsgA PUSCH transmission), theRNTI generation method may be used to distinguish an RA-RNTI related toa specific PUSCH occasion group from an RA-RNTI related to another PUSCHoccasion group.

4) When RA-RNTIs for MsgB monitoring in the 2-step RACH procedure aregenerated according to related ROs, a MsgB monitoring window may overlapwith another MsgB monitoring window related to an RO having an offset of10 ms even if the size of the MsgB monitoring window is 10 ms becausethe starting point of the MsgB monitoring window is after a time atwhich a MsgA PUSCH is transmitted, as shown in FIG. 21. Accordingly, theRNTI generation method may be used to distinguish RNTIs related tooverlapping MsgB monitoring windows. Meanwhile, the MsgA PUSCH may betransmitted after a MsgA PRACH preamble is transmitted. Accordingly, thetime position of a PUSCH resource associated with the MsgA PRACHpreamble may vary for each MsgA PRACH preamble.

In addition, Usage 3 may be applied to scenarios other than theabove-described four scenarios.

2. Embodiment 2

Hereinafter, a method of distinguishing the 4-step RACH procedure andthe 2-step RACH procedure based on a PDCCH while using an existingRA-RNTI and a method of identifying which PDCCH monitoring window is forthe PDCCH when there are overlapping PDCCH monitoring windows will bedescribed.

(1) Embodiment 2-1: Method of Using PDCCH Scrambling Sequence

An RNTI may consist of 16 bits, and a CRC scrambled to the 16 bits mayconsist of 24 bits. Accordingly, when the 16-bit RNTI is mapped, 8 bitsremain. Among the 8 bits, at least one bit may be used to scramble theCRC. For example, in addition to a commonly used RNTI, bits capable ofadditionally specifying a corresponding PDCCH may be used for CRCscrambling.

By doing so, an RAR may be distinguished from MsgB of the 2-step RACHprocedure. In addition, if the length of a monitoring window exceeds 10ms, Embodiment 2-1 may be used to distinguish which monitoring window aPDCCH received in overlapping monitoring windows is related to.

(2) Embodiment 2-2: Method of Using DMRS Sequence

To generate a DMRS sequence, an RNTI and N_(id) may be used as a seedvalue. In this case, a common RNTI is used as the seed value, anddifferent N_(id) values for specifying PDCCHs may be used to distinguishthe corresponding PDCCHs.

(3) Embodiment 2-3: Method of Using PDCCH Contents

Some of the bits included in DCI may be used to indicate that PDCCHs areused for other purposes but use the same RA-RNTI. Here, the PDCCHs forother purposes may mean different PDCCHs for distinguishing an RAR andMsgB, different PDCCHs for distinguishing an RAR of the 2-step RACHprocedure and an RAR of the 4-step RACH procedure, or different PDCCHsfor distinguishing an RAR (or MsgB) received within a predetermined time(e.g., 10 ms) from the start of a monitoring window and an RAR (or MsgB)received after the predetermined time.

On the other hand, the corresponding indicator may be included in an RARmessage or MsgB rather than the PDCCH contents.

3. Embodiment 3

Hereinafter, particular examples will be described with reference toEmbodiments 1 and 2.

(1) Embodiment 3-1: Method of Distinguishing PDCCH for RAR of 2-StepRACH Procedure and PDCCH for RAR of 4-Step RACH Procedure

An RO may be shared for the 2-step RACH procedure and the 4-step RACHprocedure. In this case, different PRACH preambles may be allocated foreach of the 2-step RACH procedure and the 4-step RACH procedure.However, if RA-RNTIs are generated based on ROs, it may be difficult forthe UE that desires to receive different responses depending on to theRACH procedure to distinguish which RACH procedure a received responseis related to.

In the 4-step RACH procedure, the UE may monitor a PDCCH for Msg2 from aslot after transmitting a PRACH preamble. Specifically, the UE maymonitor the PDCCH based on an RA-RNTI within a monitoring window of upto 10 ms included in an RAR search space indicated by the BS for PDCCHmonitoring.

On the other hand, in the 2-step RACH procedure, the UE may monitor aPDCCH for the RAR of the 2-step RACH procedure from a slot configured asDL or flexible after a lapse of a predetermined time from when the UEtransmits a MsgA PRACH preamble and a MsgA PUSCH (for example, afterPUSCH transmission or at the end of a PUSCH group).

In this case, the UE may monitor the PDCCH within a search spaceconfigured for the 2-step RAR. On the other hand, the search spaceconfigured for the 2-step RAR may be the same as a search spaceconfigured for the 4-step RACH procedure. Alternatively, the searchspace configured for the 2-step RAR may be separately designated for the2-step RACH procedure.

When the UE monitors the PDCCH for the 2-step RAR, the UE may usedifferent RNTIs based on the state of the UE. For example, when the UEis in the RRC CONNECTED state, the UE may use a C-RNTI to receive asuccess RAR, and at the same time, the UE may use an RA-RNTI to receivea fallback RAR. Alternatively, when the UE is in the RRC CONNECTEDstate, the UE may use only an RA-RNTI to receive the success RAR andfallback RAR.

On the other hand, when the UE is in the RRC IDLE/INACTIVE state, the UEmay use an RA-RNTI to receive the 2-step RAR. For example, the 2-stepRA-RNTI may be different from the 4-step RA-RNTI. As another example,the 4-step RA-RNTI and the 2-step RA-RNTI may be the same, and in thiscase, a specific bit string for the 2-step RACH procedure may be maskedto N bits that remains after CRC mapping. For example, if a CRC is 24bits and an RA-RNTI is 16 bits, 8 bits remain. Thus, the specific bitstring is masked to the remaining 8 bits, and the 2-step RAR and the4-step RAR may be distinguished based on the masked specific bit string.

Even if the PDCCH for the 2-step RAR and the PDCCH for the 4-step RARare identified by the above method, there may be a collision between2-step RA-RNTIs due to the following reasons. Monitoring of the PDCCHfor the 2-step RAR starts at the time when a PUSCH occasion (PO) istransmitted after an RO, the monitoring duration may exceed 10 ms, andthe existing RA-RNTI is repeated every 10 ms.

To solve this problem, information indicating which RO or PO the RA-RNTIis for may be indicated by a control signal (e.g., DCI) for the 2-stepRACH RAR or an RAR message. For example, the lower N bits of an SFN maybe included in the control signal or the RAR message. For example, N mayhave one of 1, 2, and 3, and the value of N may be determined accordingto the RAR monitoring window and the PDCCH search start time. Inaddition, information on a relative time elapsed from the RO may beincluded in the control signal or the RAR message. For example,information about N*10 ms from the RO may be included, and in this case,N may have a value of 1, 2, 3, 4, 5, 6, 7, or 8.

Embodiment 3-2: Method of Monitoring PDCCH for RAR when there is PRACHPreamble not Mapped to PUSCH Resource Unit (PRU) among 2-Step PRACHPreambles in Mapping of RO and PO

In the 2-step RACH procedure, the UE may map PRACH preambles of aspecific RO to PRUs of a specific PO to configure MsgA.

However, when the number of ROs is more than the number of POs, some ROsmay not be mapped to the POs. Alternatively, some PRACH preambles maynot be mapped to the PRUs. When the UE performs the 2-step RACHprocedure, the UE may transmit MsgA by selecting a PRACH preamble thatis not mapped to the PRUs at a specific time from among 2-step PRACHpreambles. In this case, the time at which the UE monitors the PDCCH forthe RAR of the 2-step RACH procedure may be after a PO on which PUSCHtransmission is expected although no PUSCH is actually transmitted.However, if a PRACH preamble where PRACH preamble-to-PRU mapping is notperformed or an RO related to the unmapped PRACH preamble is known tothe BS and UE, PDCCH monitoring may be performed from a slot after the2-step PRACH preamble is transmitted as in the existing 4-step RACHprocedure where monitoring is performed from a slot after the PRACHpreamble is transmitted. That is, the slot after transmitting the 2-stepPRACH preamble may be the start time of monitoring the PDCCH for the2-step RAR. In addition, in this case, since no PUSCH is actuallytransmitted, the BS may detect no PUSCH, and thus the UE may expect toreceive the fallback RAR.

(3) Embodiment 3-3: Method of Including Time Information in DCI or RARMessage When PDCCH Monitoring Window Exceeds 10 ms

Referring to FIG. 22, when a PDCCH is transmitted in a slot locatedwithin a range of 10 ms with respect to a RACH slot including an RO,time information included in DCI or an RAR message may be set to ‘000’.When the receiver (e.g., UE) obtains the time information of ‘000’ inthe DCI or RAR message, the receiver may recognize that thecorresponding RAR is a response to a RACH transmitted from the ROlocated within the range of 10 ms. When the PDCCH is transmitted in aslot located within a range of 10 ms to 2*10 ms, the time informationincluded in the DCI or RAR message may be set to ‘001’. The timeinformation may be configured for other time ranges in a manner similarto the above. Meanwhile, the bit size of the time information is notlimited. For example, if the time information consists of 3 bits asdescribed above, a duration of 0 to X ms (40 ms<X≤80 ms) may be dividedinto Y durations (4<Y≤8) in units of 10 ms, and it is possible toidentify which duration among 8 divided durations the PDCCH istransmitted in. In addition, if the time information consists of 5 bits,a duration of 0 to X ms (160 ms<X≤320 ms) may be divided into Ydurations (16<Y≤32) in units of 10 ms, and it is possible to identifywhich duration among 32 divided durations the PDCCH is transmitted in.

When the PDCCH is transmitted in a slot located within a range of 10 mswith respect to a slot for monitoring a Msg2 RAR, the time informationmay be set to ‘000’. When the receiver (e.g., UE) obtains the timeinformation of ‘000’, the receiver may recognize that the correspondingMsg2 RAR is a response to a RACH transmitted from an RO located withinthe range of 10 ms. When the PDCCH is transmitted in a slot locatedwithin a range of 10 ms to 2*10 ms with respect to the slot formonitoring the Msg2 RAR, the time information may be set to ‘001’. Thetime information may be configured for other time ranges in a mannersimilar to the above. Meanwhile, the bit size of the time information isnot limited. For example, if the time information consists of 3 bits asdescribed above, a duration of 0 to X ms (40ms<X≤80 ms) may be dividedinto Y durations (4<Y≤8) in units of 10 ms, and it is possible toidentify which duration among 8 divided durations the PDCCH istransmitted in. In addition, if the time information consists of 5 bits,a duration of 0 to X ms (160 ms<X≤320 ms) may be divided into Ydurations (16<Y≤32) in units of 10 ms, and it is possible to identifywhich duration among 32 divided durations the PDCCH is transmitted in.

The time information may be configured similarly to the above-describedmethod, but the reference slot may be a slot for monitoring a MsgB RAR.

The time information may be information indicating a relative differencebetween the number of a frame including the RO and the number of a frameat the time when the PDCCH is received.

(4) Embodiment 3-4: Method of Using CRC Scrambling to Distinguish DCIfor MsgB and DCI for Msg2 When Both MsgB and Msg2 Use Same RNTI

The following is extracted from Clause 7.3.2 CRC attachment of 3GPP TS38.212.

-   -   Error detection for DCI transmission may be performed through a        CRC. The entire payload for the CRC may be used to calculate CRC        parity bits. The payload bits may be defined as a₀, a₁, a₂, a₃,        . . . , a_(A−1), and parity bits may be defined as p₀, p₁, p₂,        p₃, . . . , p_(L−1), where A is the payload size, and L is the        number of parity bits. The parity bits are calculated based on        an input bit sequence of a′₀, a′₁, a′₂, a′₃, . . . , a′_(A+L−1)        and are according to Clause 5.1 of 3GPP TS 38.212. In this case,        L may be 24 bits and appended based on a generation polynomial.    -   If K=A+L, output bits of b₀, b₁, b₂, b₃, . . . , b_(K−1) may be        defined as:

b_(k)=a_(k) when k=0, 1, 2, . . . , A−1; and b_(k)=p_(k−A) when k=A,A+1, A+2, . . . , A+L−1.

-   -   After attachment, the CRC parity bits are scrambled in the form        of a bit sequence of c₀, c₁, c₂, c₃, . . . , c_(K−1) based on        the corresponding RNTI. In this case, the relationship between        c_(k) and b_(k) is defined by c_(k)=b_(k) when k=0, 1, 2, . . .        , A+7 and c_(k)=(b_(k)+x_(mti,k−A−8)) mod 2 when k=A+8, A+9,        A+10, . . . , A+23.

As described above, referring to the contents of Clause 7.3.2 of 3GPP TS38.212, when the 16-bit RNTI is scrambled to the 24-bit CRC andadditional scrambling is performed on the remaining bits, the CRC bitsmay be configured in the same way as in Equation 2 below.c_(k)=b_(k) for k=0, . . . , A−1c _(k)=(b _(k) +X _(mask,k−A)) mod 2 for k=A, . . . , A+7c _(k)=(b _(k) +x _(mti,k−A−8)) mod 2 for k=A+8, . . . , A+23  [Equation 2]

Here, previously used {0,0,0,0,0,0,0,0} may be used as Xmask. If anadditional mask is required, a bit string having at least one differentbit such as {0,1,0,1,0,1,0,1}, {0,0,0,0,0,0,0,1}, etc. may be used.

Embodiment 3-4 may be applied even when the RNTI increases to 24 bits.In this case, for a conventional RNTI with 16 bits and an RNTI usingextended bits (e.g., 24 bits), the number of scrambled bits may bedetermined based on the range of the above-described values.

4. Embodiment 4

In Embodiment 4, a time synchronization assumption between BSs includinga gNB, a mobile BS, a satellite, a vehicle, etc. in a network supportingthe 2-step RACH procedure will be described.

In particular, a time synchronization assumption used by the UE toperform handover will be described. That is, Embodiment 4 is not limitedto a system including the UE and gNB, and Embodiment 4 may be applied tovarious types of BSs and UEs including repeaters such as an integrationof access and backhaul (IAB) and a relay, and artificial satellites suchas a non-terrestrial network (NTN). Embodiment 4 may also be applied tocommunication between various UEs such as communication between vehiclesor communication between flying objects.

In the 2-step RACH procedure, the UE may transmit an MsgA PRACH preambleand an MsgA PUSCH. Upon receiving the MsgA PRACH preamble and MsgAPUSCH, the BS may attempt to detect the MsgA PRACH preamble and thenattempt to acquire information on the UE from the MsgA PUSCH. If the BSsuccessfully obtains the UE information based on the MsgA PRACH preambledetection and MsgA PUSCH decoding, the BS may transmit a success RAR tothe UE. On the other hand, when the BS detects the MsgA PRACH preamblebut fails to decode the MsgA PUSCH, the BS may transmit to the UE afallback RAR to instruct the UE to fall back to the 4-step RACHprocedure related to the successfully detected PRACH preamble.

If the BS fails in both the MsgA PRACH preamble detection and MsgA PUSCHdecoding, the BS may not transmit any RAR to the UE.

To receive the success RAR or fallback RAR transmitted by the BS, the UEmay monitor a PDCCH for MsgB based on a MsgB-RNTI. Upon detecting DCIrelated to the corresponding MsgB-RNTI, the UE may obtain a message forthe success RAR or fallback RAR from a PDSCH scheduled by the DCI.

However, when the length of a monitoring window for the UE to monitorthe PDCCH for MsgB based on the MsgB-RNTI is 10 ms or more, if differentUEs select MsgA PRACH preambles on different ROs but use the sameMsgB-RNTI, monitoring windows for PDCCH monitoring may overlap. In thiscase, there is a problem in that the UE is incapable of knowing exactlywhich RO is the detected PDCCH for the MsgA PRACH preamble is relatedto.

To solve this problem, a method of allowing UEs using the same MsgB-RNTIto distinguish an RAR related to detected DCI by transmittinginformation on the index of a frame where a corresponding RO is selectedin the DCI may be introduced. Details of the method have been describedin Embodiments 1 to 3.

In the LTE and NR systems, a frame index may be transmitted by theparameter called SFN, and the SFN is included in the PBCH. In otherwords, the SFN may be obtained by decoding the PBCH.

For example, when the UE selects a specific cell in the initial accessstage, the UE may detects a physical cell ID (PCID) from a primarysynchronization signal/secondary synchronization signal (PSS/SSS) andobtain various time information (e.g., SSB index, half frame index,etc.) including the SFN and information (e.g., RMSI CORESET, searchspace, SCS, resource block alignment, etc.) essential to receive systeminformation block type 1 (SIB1) by decoding the PBCH.

When the UE obtains RACH-related information from SIB1, if the networkindicates the 2-step RACH procedure, the UE may transmit MsgA and thenuse SFN information obtained from the PBCH decoding while monitoringMsgB.

When a primary cell of a master or secondary cell group (Spcell) isadded to the UE in dual connectivity, the UE may receive the RACHconfiguration for a RACH performed through the Spcell from a Pcell.Then, the UE may perform a RACH procedure according to the correspondingRACH configuration. In addition, when handover is instructed, the UE mayreceive the RACH configuration of a target cell through a handovercommand Then, the UE may perform a RACH procedure for the target cellbased on the corresponding RACH configuration.

If each of the RACH period and the RO to SSB association pattern periodis 10 ms or more while the UE performs the dual connectivity orhandover, the UE may need to know the SFN of the target cell to performthe RACH procedure. If the UE needs to complete the RACH procedure aswell as time/frequency tracking within an interrupt time as in thehandover, decoding of the PBCH of the target cell to obtain the SFN maybe a significant burden on the UE. When the UE needs to complete theRACH procedure within the interrupt time as in the handover in the LTEand NR systems due to the above-mentioned problems, the UE may beallowed to perform the RACH procedure without PBCH decoding in order toreduce the time delay due to the PBCH decoding and reduce the burden onthe UE caused by the PBCH decoding. That is, UE operations requiring thePBCH decoding may not be adopted.

Meanwhile, problems similar to the above may occur in the 2-step RACHprocedure if the size of a MsgB monitoring window is 10 ms or more.

To solve these problems, the method of identifying multiple ROs usingthe same MsgB-RNTI by configuring a specific time for identifying UEsusing the same MsgB-RNTI and transmitting to UEs information about atime duration from the specific time to a time when DCI is received hasbeen proposed in Embodiment 3.

According to the method proposed in Embodiment 3, the UE needs to obtainSFN information from PBCH decoding. However, when the UE needs tocomplete a RACH procedure within an interrupt time as in handover asdescribed above, a method of enabling the UE to obtain or assume an SFNrelated to a selected RO without PBCH decoding is required. Accordingly,methods of allowing the UE to assume or obtain the SFN without PBCHdecoding are proposed.

(1) Embodiment 4-1:

1) If the 2-step RACH procedure is configured in the handover process,the UE may assume that synchronization between the current cell and thetarget cell is aligned.

2) If the 2-step RACH procedure is configured in the handover processand the MsgB monitoring window size exceeds 10 ms, the UE may assumethat synchronization between the current cell and the target cell isaligned.

3) If at least one of the MsgB monitoring window for 2-step RACHcontention free random access (CFRA) and the MsgB monitoring window for2-step RACH contention based random access (CBRA) exceeds 10 ms in thehandover process, the UE may assume that synchronization between thecurrent cell and the target cell is aligned.

Hereinafter, the operation in which the UE assumes that synchronizationbetween the current cell and the target cell is aligned in Embodiment4-1 will be described in detail.

When the 2-step RACH procedure is configured during the handover to thetarget cell, the UE may assume that the absolute time difference betweena radio frame i of the current cell and a radio frame i of the targetcell is N. In this case, N may be, for example, 153600 Ts (5 ms) or76800 Ts (2.5 ms), where Ts may be 1/2048/15000 s.

Specifically, when the target cell has Lmax=4 and uses a paired orunpaired spectrum, N=153600 Ts may be applied. In addition, when thetarget cell has Lmax=8 and uses an unpaired spectrum and when the sourcecell uses a paired or unpaired spectrum, N=76800 Ts may be applied.

In other words, it may be assumed for frequency division duplex (FDD) ina band below 3 GHz in FR1 that the indices of frames of the target cellare equal to those of the current cell within a time error range of +/−5ms. In addition, it may be assumed for time division duplex (TDD) in aband below 2.8 GHz that the indices of frames of the target cell areequal to those of the current cell within a time error range of +/−5 ms.Further, for TDD in a band above 2.8 GHz in FR1, it may be assumed thatthe indices of frames of the target cell are equal to those of thecurrent cell within a time error range of +/−2.5 ms.

(2) Embodiment 4-2

If the MsgB monitoring window size for the 2-step RACH CFRA is less than10 ms and the MsgB monitoring window size for the 2-step RACH CBRA ismore than 10 ms, the UE may perform the 2-step RACH CFRA based on ahandover command. Alternatively, the UE may perform CBRA by selectingthe 4-step RACH CBRA instead of the 2-step RACH CBRA.

(3) Embodiment 4-3

When the UE performs handover, the network may inform the UE whether thenetwork is synchronous or asynchronous through a synchronizationassumption indicator. If the corresponding indicator indicates that thenetwork is synchronous and the 2-step RACH procedure is configured, theUE may perform the 2-step RACH procedure. On the other hand, if thecorresponding indicator indicates that the network is asynchronous, theUE may perform the 4-step RACH procedure rather than the 2-step RACHprocedure. However, even in this case, the UE may perform the 2-stepRACH procedure if the UE completes the handover and acquires the SFN. Insome cases, the UE may perform the 4-step RACH procedure.

(4) Embodiment 4-4

The network may provide information on the SFN of the target cell to theUE through a handover command. For example, the network may provide arelative difference between the SFN of the current cell and the SFN ofthe target cell to the UE through the handover command

5. Embodiment 5

If the BS successfully decode a MsgA PUSCH, the BS may transmit asuccess RAR to the UE based on a C-RNTI. The UE does not need to obtainan SFN because the UE receives DCI based on C-RNTI. In addition, in thiscase, the length of a monitoring window may increase relatively

However, if the BS fails to decode the MsgA PUSCH, the BS may transmit afallback RAR based on a MsgB-RNTI. In this case, if the UE receives DCIbased on the MsgB-RNTI, the UE needs to obtain information on the SFN ofthe target cell to decode SFN related information included in the DCI.

For example, when the UE receives the DCI based on the MsgB-RNTI, the UEmay compare the SFN related information included in the DCI with an SFNin which the UE transmits a MsgA PRACH preamble. If it is determinedthat the SFN included in the DCI matches or corresponds to the SFN inwhich the MsgA PRACH preamble is transmitted, the UE may perform asubsequent RACH procedure.

Here, the subsequent RACH procedure may mean that when the BSsuccessfully decodes a PUSCH and transmits a success RAR, the UEtransmits a PUCCH including HARQ-ACK information having an ACK valueindicating that the UE has successfully received MsgB. In addition, thesubsequent RACH procedure may also mean that when the BS transmits afallback RAR due to failure in PUSCH decoding, the UE performs a processto fall back to the 4-step RACH procedure.

However, as described in Embodiment 4, when the UE performs handover, itmay be difficult for the UE to obtain the SFN of the target cell if theUE performs the RACH procedure without decoding the PBCH of the targetcell.

In Embodiment 5, operation methods of allowing the UE to terminate theRACH procedure when the UE fails to acquire the SFN of the target cellwill be described. For example, if the UE does not decode the PBCHduring the handover process in order to reduce the time delay andprocessing load of the UE due to the PBCH decoding, the UE may performthe RACH procedure in a state in which the UE does not know informationabout the SFN in which the MsgA PRACH preamble is transmitted.

In other words, how the UE operates when the UE fails to obtain the SFNof the target cell will be described in Embodiment 5.

When the UE does not acquire the SFN of the target cell, the UE maytransmit MsgA. In addition, when monitoring MsgB, the UE may assume amonitoring window shorter than a monitoring window configured by thenetwork. In addition, when the UE receives DCI based on a MsgB-RNTI, theUE may decode a PDSCH scheduled by the corresponding DCI withoutchecking the validity of an SFN indicator (e.g., SFN relatedinformation) included in the DCI.

Here, the operation in which the UE does not check the validity of theSFN related information included in the DCI may mean that the UE doesnot check whether or not the SFN in which the MsgA PRACH preamble istransmitted matches and/or corresponds to the SFN related informationincluded in the DCI. Further, the operation may mean that the UE decodesthe PDSCH scheduled by the DCI and checks an RAR without checkingwhether the SFN in which the MsgA PRACH preamble is transmitted matchesand/or corresponds to the SFN related information included in the DCI.

Hereinafter, particular methods by which the UE decodes the PDSCHwithout checking the validity of the SFN related information included inthe DCI will be described.

(1) Embodiment 5-1

When the UE monitors DCI based on a C-RNTI, the UE may use the value ofa monitoring window (e.g., window length) configured for the C-RNTI asit is.

On the other hand, when the UE monitors DCI based on a MsgB-RNTI, thelength of a monitoring window may be limited to 10 ms. When receivingthe DCI based on the MsgB-RNTI, the UE may perform PDSCH decodingregardless of SFN related information included in the DCI.

When the UE does not receive a success RAR within the monitoring windowbased on the C-RNTI, the UE may retransmit MsgA or transmit Msg1 to fallback to the 4-step RACH procedure.

When the UE receives a fallback RAR based on the MsgB-RNTI, if the BStransmits the fallback RAR within the 10 ms range of the monitoringwindow, there may be no problem due to contention by the fallback RAR.In addition, in this case, there may be no problem in the PBCH decodingof the UE.

(2) Embodiment 5-2

The UE may use the length of a monitoring window configured based on aMsgB-RNTI as it is. In this case, the monitoring window may be an MsgBmonitoring window and/or an RA monitoring window. For example, if thelength of the monitoring window based on the MsgB-RNTI exceeds 10 ms,the UE may monitor DCI related to the MsgB-RNTI by assuming a monitoringwindow longer than 10 ms. In this case, the UE may ignore SFN relatedinformation included in the received DCI. That is, the UE may decode aPDSCH on a PDSCH resource indicated by the DCI, regardless of a value ofthe SFN related information.

Here, the operation in which the UE ignores the SFN related informationmay mean that the UE does not decode bits related to the SFN included inthe DCI or that even if the UE decodes the bit related to the SFNincluded in the DCI to obtain information on the SFN, the UE discardsthe decoded bits.

For example, if the UE transmits MsgA to the target cell during thehandover process but fails to acquire information on the SFN in whichthe MsgA PRACH preamble is transmitted and detects the DCI based on theMsgB-RNTI, the UE may decode the PDSCH on the PDSCH resource indicatedby the DCI regardless of the SFN related information included in theDCI.

For example, if the UE does not decode the PBCH during the handoverprocess in order to reduce the time delay and processing load of the UEdue to the PBCH decoding, the UE may transmit MsgA to the target cellwithout knowing the SFN in which the MsgA PRACH preamble is transmitted.In this case, the UE may decode the PDSCH on the PDSCH resourceindicated by the DCI regardless of the SFN related information includedin the DCI.

In addition, when the RAR obtained from the PDSCH decoding is a successRAR, the UE transmits HARQ-ACK information having an ACK value to the BSover a PUCCH. When the acquired RAR is a fallback RAR, the UE mayperform the 4-step RACH procedure.

(3) Embodiment 5-3

To perform handover to the target cell in the asynchronous network, theUE may monitor DCI within a monitoring window (e.g., a monitoring windowof 40 ms) after transmitting MsgA. When the UE receives DCI for MsgBwhere an RAPID and RNTI related parameters except for SFN related twobits are matched within the corresponding monitoring window, the UE mayproceed with a subsequent procedure until contention resolution succeedsor fails without validation of the SFN related two bits for receivingMsgB.

However, if the UE is capable of confirming that the SFN related twobits included in the DCI for MsgB do not match the least significant twobits of the SFN of a frame in which the UE transmits MsgA, the UE maynot proceed with the subsequent RACH procedure by determining that theMsgB is not valid.

In other words, according to Embodiment 5-3, if the UE detects DCI forMsgB based on a MsgB-RNTI, the UE may decode a PDSCH on a PDSCH resourceindicated by the DCI regardless of SFN related information included inthe DCI (or by ignoring the SFN related information) as described inEmbodiment 5-2.

However, if the UE knows an SFN in which MsgA is transmitted for somereason and if the UE obtains and decodes the SFN related informationincluded in the DCI, the UE may compare the SFN in which MsgA istransmitted and the SFN related information included in the DCI. If theUE knows that the SFN in which MsgA is transmitted does not match ordoes not correspond to the SFN related information included in the DCI,the UE may determine that the PDSCH received on the PDSCH resourceindicated by the DCI is not valid and thus transmit a PRACH for the4-step RACH procedure or retransmit MsgA for the 2-step RACH procedure.

That is, if the UE decodes a PBCH of the target cell for some reason orrecognizes the SFN in which MsgA is transmitted to the target cellwithout performing PBCH decoding, the UE may be capable of performingthe RACH procedure accurately by checking the validity of the SFNrelated information included in the DCI. This is because in this case,the UE may neither need to ignore the SFN related information includedin the DCI nor perform the validity check process.

(4) Embodiment 5-4

When the length of an RAR monitoring window is set more than 10 ms, ifthe UE is handed over from an asynchronous network to a target cell, theUE may assume that the length of the corresponding monitoring window isup to 10 ms.

(5) Embodiment 5-5

A handover (HO) interrupt time may be redefined for the 2-step RACHprocedure. For example, the HO interrupt time for the 2-step RACHprocedure may be set less than or equal to the existing interrupt time.

(6) Embodiment 5-6

If the UE performs PBCH decoding more than once within a HO interrupttime, the UE may perform the RACH procedure. The network may determinewhether the PBCH decoding is possible more than once within the HOinterrupt time and inform the UE of the determination by transmitting aparameter including a predetermined threshold value to the UE. If thepredetermined threshold in the corresponding parameter satisfies aspecific measurement, the UE may determine that the UE is capable ofperforming the PBCH decoding more than once within the HO interrupt timeand then perform the PBCH decoding.

(7) Embodiment 5-7

When the UE is capable of low latency PBCH decoding in an asynchronousnetwork, if a signal-to-noise (SNR) range capable of detecting a PBCH atone time (i.e., single-shot PBCH) is configured or if the correspondingSNR range is satisfied, the UE may perform PBCH decoding.

For example, the UE may perform the 2-step RACH procedure only if thePBCH detection success rate exceeds a predetermined level (e.g., 99.9%)after several attempts (e.g., one attempt).

However, for a synchronous network, the UE may perform the 2-step RACHprocedure without any conditions. If a network gives a RACH of 20 ms orlonger, the network is assumed to be synchronous. Therefore, RAN4 needsto include a condition that the RACH succeeds only in 20 ms. Forexample, second HO minimum performance may be included. That is, UEssatisfying this new condition or UEs capable of obtaining necessaryinformation before HO by decoding PBCHs of neighboring cells may performthe 2-step RACH procedure.

Details of the above-described UE capability, HO condition, newcondition, monitoring window, SFN related information, etc. areapplicable to wireless communication systems operating in unlicensedbands, and in particular, the details may be applied to the 4-step RACHprocedure and the 2-step RACH procedure.

Each of the sub-embodiments of Embodiment 5 may be implementedindependently, but the sub-embodiments may be combined. In addition, thesub-embodiments described in Embodiments 1 to 4 or 6 to 9 may beimplemented in combination with the sub-embodiments of Embodiment 5 aswell.

6. Embodiment 6

In CFRA for 2-step RACH procedure, the UE may transmit MsgA. Uponreceiving MsgA, the BS may detect a PRACH preamble and decodes a PUSCHrelated to the detected PRACH preamble. If the BS successfully detectsthe PUSCH, the BS may transmit a response thereto to the UE. In thiscase, a CRC may be masked with a C-RNTI for DCI. The UE may detect theDCI based on the C-RNTI and acquire information transmitted by the BSover a PDSCH.

Hereinafter, a method of configuring MsgA for the CFRA of the 2-stepRACH procedure will be described.

In the CFRA, the UE may be allowed to transmit only a MsgA PRACHpreamble without mapping to a PUSCH resource. Therefore, MsgA mayconsist of only a PRACH preamble.

When the UE selects the 2-stepRACH, if the channel quality (e.g., RSRP)of a SSB/CSI-RS is higher than a specific value, the UE may perform2-step RACH CFRA where the UE transmits only the PRACH preamble. If thechannel quality becomes less than or equal to the specific value, the UEmay perform 2-step RACH CBRA where the UE transmits both the PRACHpreamble and the PUSCH.

Specifically, in the conventional 4-step RACH procedure, CFRA may beperformed in two stages. When the CFRA is performed in two stages, theUE may start monitoring of an RAR after transmitting a PRACH preambleand then receive the RAR as a response to the PRACH preamble.

However, in the 2-step RACH procedure, if MsgA includes a MsgA PUSCH aswell as the MsgA PRACH preamble, the UE may perform RA monitoring aftertransmitting the MsgA PUSCH. Therefore, if the 2-step RACH CFRA isconfigured with the MsgA PRACH preamble and the MsgA PUSCH, the 2-stepRACH CFRA may require not only a time for MsgA transmission but also atime for the BS to receive and process MsgA and a time for UE to monitorrandom access. As a result, the total time required for the RACHprocedure may increase. However, it may be undesirable that the totaltime required for the RACH procedure increases when an interrupt timeneeds to be considered as in HO.

If transmission of information necessary for a PUSCH during the RACHprocedure gives a greater benefit even though the RACH time increases,it may be considered to transmit the PRACH preamble and PUSCH.Otherwise, it is undesirable that the RACH time increases.

If PUSCH related information is not indicated by parameters configuredfor the CFRA, MsgA may consist of only the PRACH preamble in the CFRA.If the PUSCH related information is indicated, MsgA may consist of theMsgA PRACH preamble and the MsgA PUSCH, and MsgA may be transmitted bythe UE to the BS.

The BS may configure a plurality of POs to the UE. In this case, theplurality of POs may have a one-to-one relationship with PRACH preamblesfor RO(s). When there is a mask index and an SSB/CSI-RS index forindicating an RO, an SSB/CSI-RS index applied to a RACH may be appliedto a PO. A RACH slot may be mapped to POs included in a PUSCH slothaving a predetermined time duration.

If the number of ROs indicated by RACH mask indices is greater than thenumber of POs, only the PRACH preamble may be transmitted on specificROs, and both the MsgA PRACH and MsgA PUSCH may be transmitted on theremaining ROs. In this case, the specific ROs may be ROs not mapped tothe POs, and the remaining ROs may be ROs mapped to the PO.

If the number of ROs is less than the number of POs, only some of thePOs may be used for MsgA transmission, and the rest may not be used. Inthis case, the POs used for MsgA transmission may be POs mapped to theRO.

7. Embodiment 7

In Embodiment 7, a method of configuring a monitoring window for MsgAincluding only a PRACH preamble will be described. In particular,Embodiment 7 may be applied to CBRA.

The UE may transmit only the PRACH preamble on a valid PRACH occasion inthe following two cases:

-   -   When the PO related to a DMRS resource is not mapped to the        PRACH preamble in a valid PRACH occasion; and    -   When the PRACH occasion is mapped to a valid PO but PUSCH        transmission is dropped due to LBT failure in a shared spectrum.

(1) Embodiment 7-1: When PO is Not Mapped to PRACH Preamble in ValidPRACH Occasion

MsgA may be configured by combining a MsgA PRACH preamble and a MsgAPUSCH. However, if the number M of available PRACH preambles included ina specific time duration is not the same as the number N of PUSCHresources (or DMRS resources), some of the PRACH preambles may not bemapped to the PUSCH resources. For example, if M=K*N is satisfied, M/KPRACH preambles may be mapped to one PUSCH resource. Accordingly, allPRACH preambles may be mapped to the PUSCH resources.

On the other hand, if M>K*N is satisfied, K=ceiling (M/L) PRACHpreambles may be mapped to one PUSCH resource. Accordingly, some PRACHpreambles may be mapped to all N PUSCH resources, but M−K*N PRACHpreambles remain. In this case, it may be considered that MsgA isconsist of only the remaining PRACH preambles.

After transmission of MsgA, it is necessary to determine the startingpoint of a monitoring window for MsgB.

When MsgA consists of the PRACH preamble and PUSCH, the MsgB monitoringwindow may be configured with respect to a PO for transmission of theMsgA PUSCH related to the MsgA PRACH preamble. However, when MsgAconsists of only the PRACH preamble, there may be no MsgA PUSCH mappedto the PRACH preamble, so that it may be difficult to configure the MsgBmonitoring window with respect to the PO.

To solve this problem, the following two methods may be considered.

Method 1) The MsgB monitoring window may be configured with respect to aPO related to transmission of a specific PUSCH although the PUSCH has nomapping relationship with the PRACH preamble.

For example, the MsgB monitoring window may be configured with respectto a PO of a PUSCH resource mapped to a specific PRACH preamble in an ROincluding the MsgA PRACH preamble.

In other words, the MsgB monitoring window may start at the first symbolof the earliest CORESET after the last symbol of a PO related to PUSCHtransmission corresponding to the PRACH preamble in a valid PRACHoccasion.

As another example, the MsgB monitoring window may be configured withrespect to a specific PO (e.g., the first or last PO among valid POs)among POs included in a PUSCH slot designated based on a RACH slotincluding the MsgA PRACH preamble.

Method 2) The MsgB monitoring window may be configured with respect toan RO related to PRACH preamble transmission.

In other words, the MsgB monitoring window may start at the first symbolof the earliest CORESET after the last symbol of a PRACH occasionrelated to PRACH transmission.

(2) Embodiment 7-2: When PUSCH Transmission is Dropped Due to LBTFailure

The MsgB monitoring window may be configured with respect to a PO inwhich PUSCH transmission related the PRACH preamble is attempted.

In other words, the MsgB monitoring window may start at the first symbolof the earliest CORESET after the last symbol of a PO on which PUSCHtransmission is attempted.

8. Embodiment 8

In Embodiment 8, a case in which the network detects a PRACH preamblewithout decoding a PUSCH will be described. In this case, the networkoperation may be considered to be equivalent to reception of Msg1, sothat the network may provide the UE with the necessary information in anRAR. If the UE supports the 2-step RACH procedure, the UE maycontinuously attempt to decode a PDCCH for MsgB until detecting MsgB.Provision of information in the RAR may not be burdensome for the UE.That is, considering the relationship with MsgB, the RAR may be reusedfor PUSCH decoding failure or fallback mechanisms.

(1) Embodiment 8-1: Indication of PRACH Preamble Detection Success andPUSCH Decoding Failure in RAR

Upon receiving MsgA (PRACH preamble+PUSCH) transmitted by the UE in the2-step RACH procedure, the BS may perform PRACH preamble detection andPUSCH decoding. When the BS successfully detects the PRACH preamble, theBS may decode the PUSCH related to the PRACH preamble.

In addition, when the BS determines through a CRC check that the BSsuccessfully receives information bits or when the BS fails to restorethe information bits, the BS may transmit information about the PRACHpreamble, which the BS has successfully detected, to the UE in an RAR.The BS may transmit the RAPID of the detected PRACH preamble to the UE.

When the BS fails to decode the PUSCH, the BS may transmit a UL grantrelated to the corresponding RAPID, a timing advanced (TA) command,TC-RNTI, and the like. On the other hand, when the BS successfullydecodes the PUSCH, the BS may inform the UE of the success or failure ofthe PUSCH decoding by using some bits and/or some code points includedin the RAR message. For example, the BS may inform the UE of the successor failure of the PUSCH decoding by using some states among variousstates indicated by bits of the UL grant.

The UE may monitor a PDCCH based on an RA-RNTI and receive the RARmessage based on the PDCCH. In addition, the UE may check the RAPID ofthe PRACH preamble transmitted by the UE from the RAR message and alsocheck whether the RAPID is successfully detected and whether the PUSCHdecoding is successful. If the UE confirms that the RAPID detection issuccessful and that the PUSCH decoding is successful, the UE may obtainthe TA command and TC-RNTI and use them to monitor a MsgB PDCCH to betransmitted later. The obtained TA command may be used for ULtransmission.

On the other hand, if the UE confirms that the RAPID detection issuccessful but the PUSCH decoding fails, the UE may obtain the TAcommand, TC-RNTI and/or UL grant, etc., and then transmit Msg3.

If the UE confirms that the PRACH preamble detection is not successful,the UE may retransmit MsgA of the 2-step RACH procedure or transmit Msg1(i.e., PRACH preamble) by falling back to the 4-step RACH procedure.

If the UE does not receive the RAR within an RAR monitoring window, theUE may retransmit MsgA of the 2-step RACH procedure after the RARmonitoring window ends. Alternatively, the UE may fall back to the4-step RACH procedure and transmit Msg1 (i.e., PRACH preamble).

(2) Embodiment 8-2: Indication of PRACH Preamble Detection Success inRAR and Indication of Fallback to Msg3 of 4-step RACH Procedure in MsgB

In the 2-step RACH procedure, the UE may transmit an MsgA PRACH preambleand an MsgA PUSCH. After transmitting the MsgA PRACH preamble, the UEmay receive a PDCCH for an RAR in an RAR monitoring window. In addition,after transmitting the MsgA PUSCH, the UE may receive a PDCCH for MsgBin a monitoring window for MsgB.

In this case, the starting point of the RAR monitoring window may beearlier than the monitoring window for MsgB. Also, the length of the RARmonitoring window may be different from the length of the monitoringwindow for MsgB. Meanwhile, the RAR monitoring window and the monitoringwindow for MsgB may partially overlap.

Upon receiving the MsgA PRACH preamble and the MsgA PUSCH transmitted bythe UE, the BS may perform PRACH preamble detection and PUSCH decoding.If the BS successfully detects the PRACH preamble, the BS may inform theUE whether or not the PRACH preamble is successfully detected in theRAR. The RAR contents may include an RAPID, a TA, a UL grant, and/or aTC-RNTI. In the 2-step RACH procedure, an indicator indicating whetherPRACH preamble detection is successful may be transmitted together withthe RAPID.

For example, the BS may transmit information on the success or failureof the PRACH preamble detection to the UE by using some bits or somecode points of the RAR message. Specifically, the BS may transmit theinformation on the success or failure of the PRACH preamble detection tothe UE by using some states among various states indicated by bits ofthe UL grant. In addition, the BS may also transmit the TA and/orTC-RNTI to the UE. If the BS transmits the TA, TC-RNTI, etc. in MsgBrather than the RAR, bits for the TA and TC-RNTI may be reserved or usedfor other purposes.

When the UE obtains the RAR based on RAR monitoring, the UE may checkthe RAPID. If the UE confirms that the PRACH preamble detection has beensuccessful, the UE may continue monitoring the PDCCH for MsgB until themonitoring window for MsgB ends even after the RAR monitoring windowends.

If the UE does not receive a message related to the RAPID within the RARmonitoring window, the UE may retransmit MsgA or fall back to the 4-stepRACH procedure to perform the RACH again. Alternatively, the UE mayattempt to access a new cell by discovering another cell ID.

When the BS receives the MsgA PUSCH transmitted by the UE andsuccessfully detects the PUSCH, the BS may transmit a message forperforming a contention resolution procedure to the UE in MsgB.

If the BS fails to decode the PUSCH, the BS may transmit a UL grant forMsg3 transmission to the UE in MsgB. If the TA, TC-RNTI, etc. aretransmitted to the UE in the RAR message, the TA, TC-RNTI, etc. may notbe transmitted in MsgB. On the contrary, if the TA, TC-RNTI, etc. arenot transmitted in the RAR message, the TA, TC-RNTI, etc. may betransmitted to the UE in MsgB. For example, if MsgB is transmittedbefore the RAR, if only MsgB is transmitted, or if the TA, TC-RNTI, etc.are not included in the 2-step RACH RAR, the TA, TC-RNTI, etc. may betransmitted to the UE in MsgB.

Upon confirming the detection of the PRACH preamble from the RAR, the UEmay continuously perform monitoring of MsgB. Upon receiving MsgB, the UEmay perform the contention resolution procedure or may transmit Msg3 tothe BS.

9. Embodiment 9

If the UE does not receive MsgB within a monitoring window for MsgB, theUE may retransmit MsgA. The above procedure is similar to retransmissionof Msg1 when the UE is incapable of receiving an RAR in LTE.

In this case, how to configure the monitoring window for MsgB and atimer therefor needs to be discussed. According to Embodiment 9, since aPRACH preamble and a PUSCH are transmitted in MsgA, the starting pointof the monitoring window for MsgB may be later than the starting pointof an RAR monitoring window as shown in FIG. 21.

It is obvious that each of the examples of the proposed methods may alsobe included as one implementation method of the present disclosure, andthus each example may be regarded as a kind of proposed method. Althoughthe above-described embodiments may be implemented independently, someof the embodiments may be combined and implemented. In addition, it maybe regulated that information on whether the embodiments are applied orinformation on rules related to the embodiments is transmitted from theBS to the UE in a predefined signal such as physical layer signaling orhigher layer signaling.

The various details, functions, procedures, proposals, methods, and/oroperational flowcharts described above in this document may be appliedto a variety of fields that require wireless communication/connection(e.g., 5G) between devices.

Hereinafter, a description will be given in detail with reference todrawings. In the following drawings/descriptions, the same referencenumerals may denote the same or corresponding hardware blocks, softwareblocks, or functional blocks unless specified otherwise.

FIG. 23 illustrates a communication system 1 applied to the presentdisclosure.

Referring to FIG. 23, the communication system 1 applied to the presentdisclosure includes wireless devices, BSs, and a network. A wirelessdevice is a device performing communication using radio accesstechnology (RAT) (e.g., 5G NR (or New RAT) or LTE), also referred to asa communication/radio/5G device. The wireless devices may include, notlimited to, a robot 100 a, vehicles 100 b-1 and 100 b-2, an extendedreality (XR) device 100 c, a hand-held device 100 d, a home appliance100 e, an IoT device 100 f, and an artificial intelligence (AI)device/server 400. For example, the vehicles may include a vehiclehaving a wireless communication function, an autonomous driving vehicle,and a vehicle capable of vehicle-to-vehicle (V2V) communication. Herein,the vehicles may include an unmanned aerial vehicle (UAV) (e.g., adrone). The XR device may include an augmented reality (AR)/virtualreality (VR)/mixed reality (MR) device and may be implemented in theform of a head-mounted device (HMD), a head-up display (HUD) mounted ina vehicle, a television (TV), a smartphone, a computer, a wearabledevice, a home appliance, a digital signage, a vehicle, a robot, and soon. The hand-held device may include a smartphone, a smart pad, awearable device (e.g., a smart watch or smart glasses), and a computer(e.g., a laptop). The home appliance may include a TV, a refrigerator, awashing machine, and so on. The IoT device may include a sensor, a smartmeter, and so on. For example, the BSs and the network may beimplemented as wireless devices, and a specific wireless device 200 amay operate as a BS/network node for other wireless devices.

The wireless devices 100 a to 100 f may be connected to the network 300via the BSs 200. An AI technology may be applied to the wireless devices100 a to 100 f, and the wireless devices 100 a to 100 f may be connectedto the AI server 400 via the network 300. The network 300 may beconfigured using a 3G network, a 4G (e.g., LTE) network, or a 5G (e.g.,NR) network. Although the wireless devices 100 a to 100 f maycommunicate with each other through the BSs 200/network 300, thewireless devices 100 a to 100 f may perform direct communication (e.g.,sidelink communication) with each other without intervention of theBSs/network. For example, the vehicles 100 b-1 and 100 b-2 may performdirect communication (e.g. V2V/vehicle-to-everything (V2X)communication). The IoT device (e.g., a sensor) may perform directcommunication with other IoT devices (e.g., sensors) or other wirelessdevices 100 a to 100 f.

Wireless communication/connections 150 a, 150 b, and 150 c may beestablished between the wireless devices 100 a to 100 f/BS 200 andbetween the BSs 200. Herein, the wireless communication/connections maybe established through various RATs (e.g., 5G NR) such as UL/DLcommunication 150 a, sidelink communication 150 b (or, D2Dcommunication), or inter-BS communication (e.g. relay or integratedaccess backhaul (IAB)). Wireless signals may be transmitted and receivedbetween the wireless devices, between the wireless devices and the BSs,and between the BSs through the wireless communication/connections 150a, 150 b, and 150 c. For example, signals may be transmitted and receivedon various physical channels through the wirelesscommunication/connections 150 a, 150 b and 150 c. To this end, at leasta part of various configuration information configuring processes,various signal processing processes (e.g., channel encoding/decoding,modulation/demodulation, and resource mapping/demapping), and resourceallocation processes, for transmitting/receiving wireless signals, maybe performed based on the various proposals of the present disclosure.

FIG. 24 illustrates wireless devices applicable to the presentdisclosure.

Referring to FIG. 24, a first wireless device 100 and a second wirelessdevice 200 may transmit wireless signals through a variety of RATs(e.g., LTE and NR). {The first wireless device 100 and the secondwireless device 200} may correspond to {the wireless device 100 x andthe BS 200} and/or {the wireless device 100 x and the wireless device100 x} of FIG. 23.

The first wireless device 100 may include one or more processors 102 andone or more memories 104, and further include one or more transceivers106 and/or one or more antennas 108. The processor(s) 102 may controlthe memory(s) 104 and/or the transceiver(s) 106 and may be configured toimplement the descriptions, functions, procedures, proposals, methods,and/or operation flowcharts disclosed in this document. For example, theprocessor(s) 102 may process information in the memory(s) 104 togenerate first information/signals and then transmit wireless signalsincluding the first information/signals through the transceiver(s) 106.The processor(s) 102 may receive wireless signals including secondinformation/signals through the transceiver(s) 106 and then storeinformation obtained by processing the second information/signals in thememory(s) 104. The memory(s) 104 may be connected to the processor(s)102 and may store various pieces of information related to operations ofthe processor(s) 102. For example, the memory(s) 104 may store softwarecode including instructions for performing all or a part of processescontrolled by the processor(s) 102 or for performing the descriptions,functions, procedures, proposals, methods, and/or operation flowchartsdisclosed in this document. The processor(s) 102 and the memory(s) 104may be a part of a communication modem/circuit/chip designed toimplement RAT (e.g., LTE or NR). The transceiver(s) 106 may be connectedto the processor(s) 102 and transmit and/or receive wireless signalsthrough the one or more antennas 108. Each of the transceiver(s) 106 mayinclude a transmitter and/or a receiver. The transceiver(s) 106 may beinterchangeably used with radio frequency (RF) unit(s). In the presentdisclosure, the wireless device may be a communicationmodem/circuit/chip.

Hereinafter, a description will be given of instructions and/oroperations controlled by the processor(s) 102 and stored in thememory(s) 104 of the first wireless device 100 according to anembodiment of the present disclosure.

While the following operations are described in the context of controloperations of the processor(s) 102 from the perspective of theprocessor(s) 102, software code for performing the operations may bestored in the memory(s) 104.

Specifically, the processor(s) 102 may control to transmit MsgA to theBS. In this case, MsgA may include only a PRACH or may include a PUSCHas well as the PRACH. When MsgA includes both the PRACH and PUSCH, theprocessor(s) 102 may transmit the PUSCH after transmitting the PRACH.

In this case, the processor(s) 102 may transmit the PRACH while knowingan SFN for transmitting the PRACH or may transmit the PRACH withoutknowing the SFN for transmitting the PRACH. Details thereof may be foundin the above-described embodiments.

The processor(s) 102 may control to monitor and receive DCI schedulingMsgB. The processor(s) 102 may descramble a CRC from the DCI based on aMsgB-RNTI. Upon confirming the CRC, the processor(s) 102 may decodeinformation bits included in the DCI.

The processor(s) 102 may decode lower two bits for the index of an SFNin the DCI and then compare the lower two bits with lower two bits forthe index of the SFN for transmitting the PRACH.

However, if the processor(s) 102 controls to transmit the PRACH withoutknowing the SFN for transmitting the PRACH, the processor(s) 102 may notcompare the lower two bits for the SFN included in the DCI and the lowertwo bits for the SFN for transmitting the PRACH.

Details thereof may be found in the above-described embodiments.

The processor(s) 102 may control to receive a PDSCH for an RAR based onthe DCI. In this case, the processor(s) 102 may receive the PDSCHaccording to the result of comparing the lower two bits for the SFNincluded in the DCI and the lower two bits for the SFN for transmittingthe PRACH. On the other hand, the processor(s) 102 may control toreceive the PDSCH regardless of the result of comparing the lower twobits for the SFN included in the DCI and the lower two bits for the SFNfor transmitting the PRACH.

In addition, the processor(s) 102 may control to receive the PDSCH orperform other operations instead of receiving the PDSCH, depending onwhether the processor(s) 102 is capable of comparing the lower two bitsfor the SFN included in DCI and the lower two bits for the SFN fortransmitting the PRACH and/or according to the comparison result.

The operations of the processor(s) 102 depending on whether theprocessor(s) 102 is capable of comparing the lower two bits for the SFNincluded in the DCI and the lower two bits for the SFN for transmittingthe PRACH and/or according to the comparison result may be based on theabove-described embodiments.

The processor(s) 102 may control to transmit a UL signal based on thePDSCH. In this case, the UL signal transmitted by the processor(s) 102may vary depending on the RAR of the PDSCH and depending on whether thePDSCH is received. For example, if the RAR is a fallback RAR, theprocessor(s) 102 may control to transmit the PRACH for the Type-1 RACHprocedure. As another example, if the RAR is a success RAR, theprocessor(s) 102 may control to transmit a PUCCH by including HARQ-ACKinformation corresponding to an ACK in the PUCCH.

If the processor(s) 102 does not receive the PDSCH, the processor(s) 102may control to transmit the PRACH according to the Type-1 RACH procedureor transmit (or retransmit) the PRACH and PUSCH according to the Type-2RACH procedure.

The operations of the processor(s) 102 may be based on one or more ofthe above-described embodiments. That is, the operations of theprocessor(s) 102 may be performed based on any one of theabove-described embodiments or any combination of two or more of theabove-described embodiments.

Hereinafter, a description will be given of instructions and/oroperations controlled by processor(s) 202 and stored in memory(s) 204 ofthe second wireless device 200 according to an embodiment of the presentdisclosure.

While the following operations are described in the context of controloperations of the processor(s) 202 from the perspective of theprocessor(s) 202, software code for performing the operations may bestored in the memory(s) 204.

The processor(s) 202 may control to receive MsgA from the UE. In thiscase, MsgA may include only a PRACH or may include a PUSCH as well asthe PRACH. When MsgA includes both the PRACH and PUSCH, the processor(s)202 may control to receive the PUSCH after receiving the PRACH.

The processor(s) 202 may control to decode MsgA and transmit DCI havinga CRC scrambled by a MsgB-RNTI to the UE based on the decoding result.

The processor(s) 202 may control to transmit a PDSCH for an RAR based onthe DCI. If the processor(s) 202 detects both the PRACH and PUSCH, theRAR may be a success RAR. If the processor(s) 202 detects only the PRACHand does not detect the PUSCH, the RAR may be a fallback RAR. If theprocessor(s) 202 does not detect both the PRACH and PUSCH, theprocessor(s) 202 may control to not transmit the DCI and PDSCH.

If the processor(s) 202 transmits the PDSCH, the processor(s) 202 maycontrol to receive a UL signal based on the PDSCH. In this case, the ULsignal may vary depending on the RAR of the PDSCH and depending onwhether the UE receives the PDSCH. For example, if the RAR is thefallback RAR, the processor(s) 202 may control to receive the PRACH forthe Type-1 RACH procedure. As another example, if the RAR is the successRAR, the processor(s) 202 may control to receive a PUCCH includingHARQ-ACK information corresponding to an ACK.

If the UE does not receive the PDSCH, the processor(s) 202 may controlto receive the PRACH according to the Type-1 RACH procedure or receive(or receive again) the PRACH and PUSCH according to the Type-2 RACHprocedure.

The above-described operations of the processor(s) 202 may be based onone or more of the above-described embodiments. That is, the operationsof the processor(s) 202 may be performed based on any one of theabove-described embodiments or any combination of two or more of theabove-described embodiments.

Now, hardware elements of the wireless devices 100 and 200 will bedescribed in greater detail. One or more protocol layers may beimplemented by, not limited to, one or more processors 102 and 202. Forexample, the one or more processors 102 and 202 may implement one ormore layers (e.g., functional layers such as physical (PHY), mediumaccess control (MAC), radio link control (RLC), packet data convergenceprotocol (PDCP), RRC, and service data adaptation protocol (SDAP)). Theone or more processors 102 and 202 may generate one or more protocoldata units (PDUs) and/or one or more service data Units (SDUs) accordingto the descriptions, functions, procedures, proposals, methods, and/oroperation flowcharts disclosed in this document. The one or moreprocessors 102 and 202 may generate messages, control information, data,or information according to the descriptions, functions, procedures,proposals, methods, and/or operation flowcharts disclosed in thisdocument and provide the messages, control information, data, orinformation to one or more transceivers 106 and 206. The one or moreprocessors 102 and 202 may generate signals (e.g., baseband signals)including PDUs, SDUs, messages, control information, data, orinformation according to the descriptions, functions, procedures,proposals, methods, and/or operation flowcharts disclosed in thisdocument and provide the generated signals to the one or moretransceivers 106 and 206. The one or more processors 102 and 202 mayreceive the signals (e.g., baseband signals) from the one or moretransceivers 106 and 206 and acquire the PDUs, SDUs, messages, controlinformation, data, or information according to the descriptions,functions, procedures, proposals, methods, and/or operation flowchartsdisclosed in this document.

The one or more processors 102 and 202 may be referred to ascontrollers, microcontrollers, microprocessors, or microcomputers. Theone or more processors 102 and 202 may be implemented by hardware,firmware, software, or a combination thereof. For example, one or moreapplication specific integrated circuits (ASICs), one or more digitalsignal processors (DSPs), one or more digital signal processing devices(DSPDs), one or more programmable logic devices (PLDs), or one or morefield programmable gate arrays (FPGAs) may be included in the one ormore processors 102 and 202. The descriptions, functions, procedures,proposals, methods, and/or operation flowcharts disclosed in thisdocument may be implemented using firmware or software, and the firmwareor software may be configured to include the modules, procedures, orfunctions. Firmware or software configured to perform the descriptions,functions, procedures, proposals, methods, and/or operation flowchartsdisclosed in this document may be included in the one or more processors102 and 202 or may be stored in the one or more memories 104 and 204 andexecuted by the one or more processors 102 and 202. The descriptions,functions, procedures, proposals, methods, and/or operation flowchartsdisclosed in this document may be implemented using firmware or softwarein the form of code, an instruction, and/or a set of instructions.

The one or more memories 104 and 204 may be connected to the one or moreprocessors 102 and 202 and store various types of data, signals,messages, information, programs, code, instructions, and/or commands Theone or more memories 104 and 204 may be configured to include read-onlymemories (ROMs), random access memories (RAMs), electrically erasableprogrammable read-only memories (EPROMs), flash memories, hard drives,registers, cash memories, computer-readable storage media, and/orcombinations thereof. The one or more memories 104 and 204 may belocated at the interior and/or exterior of the one or more processors102 and 202. The one or more memories 104 and 204 may be connected tothe one or more processors 102 and 202 through various technologies suchas wired or wireless connection.

The one or more transceivers 106 and 206 may transmit user data, controlinformation, and/or wireless signals/channels, mentioned in the methodsand/or operation flowcharts of this document, to one or more otherdevices. The one or more transceivers 106 and 206 may receive user data,control information, and/or wireless signals/channels, mentioned in thedescriptions, functions, procedures, proposals, methods, and/oroperation flowcharts disclosed in this document, from one or more otherdevices. For example, the one or more transceivers 106 and 206 may beconnected to the one or more processors 102 and 202 and transmit andreceive wireless signals. For example, the one or more processors 102and 202 may perform control so that the one or more transceivers 106 and206 may transmit user data, control information, or wireless signals toone or more other devices. The one or more processors 102 and 202 mayperform control so that the one or more transceivers 106 and 206 mayreceive user data, control information, or wireless signals from one ormore other devices. The one or more transceivers 106 and 206 may beconnected to the one or more antennas 108 and 208 and the one or moretransceivers 106 and 206 may be configured to transmit and receive userdata, control information, and/or wireless signals/channels, mentionedin the descriptions, functions, procedures, proposals, methods, and/oroperation flowcharts disclosed in this document, through the one or moreantennas 108 and 208. In this document, the one or more antennas may bea plurality of physical antennas or a plurality of logical antennas(e.g., antenna ports). The one or more transceivers 106 and 206 mayconvert received wireless signals/channels from RF band signals intobaseband signals in order to process received user data, controlinformation, and wireless signals/channels using the one or moreprocessors 102 and 202. The one or more transceivers 106 and 206 mayconvert the user data, control information, and wirelesssignals/channels processed using the one or more processors 102 and 202from the baseband signals into the RF band signals. To this end, the oneor more transceivers 106 and 206 may include (analog) oscillators and/orfilters.

FIG. 25 illustrates another example of a wireless device applied to thepresent disclosure. The wireless device may be implemented in variousforms according to a use case/service (refer to FIG. 23).

Referring to FIG. 25, wireless devices 100 and 200 may correspond to thewireless devices 100 and 200 of FIG. 24 and may be configured to includevarious elements, components, units/portions, and/or modules. Forexample, each of the wireless devices 100 and 200 may include acommunication unit 110, a control unit 120, a memory unit 130, andadditional components 140. The communication unit 110 may include acommunication circuit 112 and transceiver(s) 114. For example, thecommunication circuit 112 may include the one or more processors 102 and202 and/or the one or more memories 104 and 204 of FIG. 29. For example,the transceiver(s) 114 may include the one or more transceivers 106 and206 and/or the one or more antennas 108 and 208 of FIG. 29. The controlunit 120 is electrically connected to the communication unit 110, thememory 130, and the additional components 140 and provides overallcontrol to the wireless device. For example, the control unit 120 maycontrol an electric/mechanical operation of the wireless device based onprograms/code/instructions/information stored in the memory unit 130.The control unit 120 may transmit the information stored in the memoryunit 130 to the outside (e.g., other communication devices) via thecommunication unit 110 through a wireless/wired interface or store, inthe memory unit 130, information received through the wireless/wiredinterface from the outside (e.g., other communication devices) via thecommunication unit 110.

The additional components 140 may be configured in various mannersaccording to type of the wireless device. For example, the additionalcomponents 140 may include at least one of a power unit/battery,input/output (I/O) unit, a driving unit, and a computing unit. Thewireless device may be implemented in the form of, not limited to, therobot (100 a of FIG. 23), the vehicles (100 b-1 and 100 b-2 of FIG. 23),the XR device (100 c of FIG. 23), the hand-held device (100 d of FIG.22), the home appliance (100 e of FIG. 23), the IoT device (100 f ofFIG. 23), a digital broadcasting terminal, a hologram device, a publicsafety device, an MTC device, a medical device, a FinTech device (or afinance device), a security device, a climate/environment device, the AIserver/device (400 of FIG. 23), the BSs (200 of FIG. 23), a networknode, or the like. The wireless device may be mobile or fixed accordingto a use case/service.

In FIG. 25, all of the various elements, components, units/portions,and/or modules in the wireless devices 100 and 200 may be connected toeach other through a wired interface or at least a part thereof may bewirelessly connected through the communication unit 110. For example, ineach of the wireless devices 100 and 200, the control unit 120 and thecommunication unit 110 may be connected by wire and the control unit 120and first units (e.g., 130 and 140) may be wirelessly connected throughthe communication unit 110. Each element, component, unit/portion,and/or module in the wireless devices 100 and 200 may further includeone or more elements. For example, the control unit 120 may beconfigured with a set of one or more processors. For example, thecontrol unit 120 may be configured with a set of a communication controlprocessor, an application processor, an electronic control unit (ECU), agraphical processing unit, and a memory control processor. In anotherexample, the memory 130 may be configured with a RAM, a dynamic RAM(DRAM), a ROM, a flash memory, a volatile memory, a non-volatile memory,and/or a combination thereof.

The implementation example of FIG. 25 will hereinafter be described withreference to the attached drawings.

FIG. 26 is a block diagram illustrating a hand-held device 100 to whichanother embodiment of the present disclosure may be applied. Thehand-held device may include a smartphone, a tablet (also called asmartpad), a wearable device (e.g., a smartwatch or smart glasses), anda portable computer (e.g., a laptop). The hand-held device 100 may bereferred to as a mobile station (MS), a user terminal (UT), a mobilesubscriber station (MSS), a subscriber station (SS), an advanced mobilestation (AMS), or a wireless terminal (WT).

Referring to FIG. 26, the hand-held device 100 may include an antennaunit 108, a communication unit 110, a control unit 120, a memory unit130, a power supply unit 140 a, an interface unit 140 b, and aninput/output (I/O) unit 140 c. The antenna unit 108 may be configured asa part of the communication unit 110. The blocks 110 to 130/140 a to 140c correspond to the blocks 110 to 130/140 of FIG. 25, respectively.

The communication unit 110 may transmit and receive signals (e.g., dataand control signals) to and from another wireless device and a BS. Thecontrol unit 120 may perform various operations by controlling elementsof the hand-held device 100. The control unit 120 may include anapplication processor (AP). The memory unit 130 may storedata/parameters/programs/code/commands required for operation of thehand-held device 100. Further, the memory unit 130 may storeinput/output data/information. The power supply unit 140 a may supplypower to the hand-held device 100, and include a wired/wireless chargingcircuit and a battery. The interface unit 140 b may support connectionbetween the hand-held device and other external devices. The interfaceunit 140 b may include various ports (e.g., an audio I/O port and avideo I/O port) for connection to external devices. The I/O unit 140 cmay receive or output video information/signal, audioinformation/signal, data, and/or user-input information. The I/O unit140 c may include a camera, a microphone, a user input unit, a display140 d, a speaker, and/or a haptic module.

For example, for data communication, the I/O unit 140 c may acquireinformation/signals (e.g., touch, text, voice, images, and video)received from the user and store the acquired information/signals in thememory unit 130. The communication unit 110 may convert theinformation/signals into radio signals and transmit the radio signalsdirectly to another device or to a BS. Further, the communication unit110 may receive a radio signal from another device or a BS and thenrestore the received radio signal to original information/signal. Therestored information/signal may be stored in the memory unit 130 andoutput in various forms (e.g., text, voice, an image, video, and ahaptic effect) through the I/O unit 140 c.

FIG. 27 illustrates a vehicle or an autonomous driving vehicle appliedto the present disclosure. The vehicle or autonomous driving vehicle maybe implemented as a mobile robot, a car, a train, a manned/unmannedaerial vehicle (AV), a ship, or the like.

Referring to FIG. 27, a vehicle or autonomous driving vehicle 100 mayinclude an antenna unit 108, a communication unit 110, a control unit120, a driving unit 140 a, a power supply unit 140 b, a sensor unit 140c, and an autonomous driving unit 140 d. The antenna unit 108 may beconfigured as a part of the communication unit 110. The blocks110/130/140 a to 140 d correspond to the blocks 110/130/140 of FIG. 24,respectively.

The communication unit 110 may transmit and receive signals (e.g., dataand control signals) to and from external devices such as othervehicles, BSs (e.g., gNBs and road side units), and servers. The controlunit 120 may perform various operations by controlling elements of thevehicle or the autonomous driving vehicle 100. The control unit 120 mayinclude an ECU. The driving unit 140 a may enable the vehicle or theautonomous driving vehicle 100 to drive on a road. The driving unit 140a may include an engine, a motor, a powertrain, a wheel, a brake, asteering device, and so on. The power supply unit 140 b may supply powerto the vehicle or the autonomous driving vehicle 100 and include awired/wireless charging circuit, a battery, and so on. The sensor unit140 c may acquire information about a vehicle state, ambient environmentinformation, user information, and so on. The sensor unit 140 c mayinclude an inertial measurement unit (IMU) sensor, a collision sensor, awheel sensor, a speed sensor, a slope sensor, a weight sensor, a headingsensor, a position module, a vehicle forward/backward sensor, a batterysensor, a fuel sensor, a tire sensor, a steering sensor, a temperaturesensor, a humidity sensor, an ultrasonic sensor, an illumination sensor,a pedal position sensor, and so on. The autonomous driving unit 140d mayimplement technology for maintaining a lane on which the vehicle isdriving, technology for automatically adjusting speed, such as adaptivecruise control, technology for autonomously driving along a determinedpath, technology for driving by automatically setting a route if adestination is set, and the like.

For example, the communication unit 110 may receive map data, trafficinformation data, and so on from an external server. The autonomousdriving unit 140d may generate an autonomous driving route and a drivingplan from the obtained data. The control unit 120 may control thedriving unit 140a such that the vehicle or autonomous driving vehicle100 may move along the autonomous driving route according to the drivingplan (e.g., speed/direction control). During autonomous driving, thecommunication unit 110 may aperiodically/periodically acquire recenttraffic information data from the external server and acquiresurrounding traffic information data from neighboring vehicles. Duringautonomous driving, the sensor unit 140 c may obtain information about avehicle state and/or surrounding environment information. The autonomousdriving unit 140 d may update the autonomous driving route and thedriving plan based on the newly obtained data/information. Thecommunication unit 110 may transfer information about a vehicleposition, the autonomous driving route, and/or the driving plan to theexternal server. The external server may predict traffic informationdata using AI technology based on the information collected fromvehicles or autonomous driving vehicles and provide the predictedtraffic information data to the vehicles or the autonomous drivingvehicles.

The embodiments of the present disclosure described herein below arecombinations of elements and features of the present disclosure. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent disclosure may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent disclosure may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It will beobvious to those skilled in the art that claims that are not explicitlycited in each other in the appended claims may be presented incombination as an embodiment of the present disclosure or included as anew claim by a subsequent amendment after the application is filed.

In the embodiments of the present disclosure, a description is madecentering on a data transmission and reception relationship among a BS,a relay, and an MS. In some cases, a specific operation described asperformed by the BS may be performed by an upper node of the BS. Namely,it is apparent that, in a network comprised of a plurality of networknodes including a BS, various operations performed for communicationwith an MS may be performed by the BS, or network nodes other than theBS. The term ‘BS’ may be replaced with the term ‘fixed station’, ‘NodeB’, ‘enhanced Node B (eNode B or eNB)’, ‘access point’, etc.

Those skilled in the art will appreciate that the present disclosure maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent disclosure. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of thedisclosure should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

The method of performing a random access channel (RACH) procedure andapparatus therefor have been described based on the 5th generation (5G)new radio access technology (new RAT) system, but the method andapparatus are applicable to various wireless communication systemsincluding the 5G NR system.

The invention claimed is:
 1. A method of transmitting an uplink signalby a user equipment (UE) in a wireless communication system, the methodcomprising: transmitting a physical random access channel (PRACH);detecting downlink control information (DCI) in response to the PRACHduring a window having a length exceeding 10 ms; receiving a physicaldownlink shared channel (PDSCH) within the window based on the DCI, andbased on the UE being incapable of checking whether two bits of a firstsystem frame number (SFN) included in the DCI are the same as two bitsof a second SFN in which the PRACH is transmitted: transmitting theuplink signal based on the PDSCH regardless of whether the two bits ofthe first SFN are the same as the two bits of the second SFN.
 2. Themethod of claim 1, wherein based on the UE being capable of checkingwhether the two bits of the first SFN are the same as the two bits ofthe second SFN: transmitting the uplink signal based on the PDSCH andbased on the UE confirming that the two bits for the first SFN are thesame as the two bits for the second SFN.
 3. The method of claim 1,wherein the DCI is scrambled by a MsgB-Radio Network TemporaryIdentifier (RNTI).
 4. A user equipment (UE) configured to transmit anuplink signal in a wireless communication system, the UE comprising: atleast one transceiver; at least one processor; and at least one memoryoperably connected to the at least one processor and configured to storeinstructions that, when executed, cause the at least one processor toperform operations comprising: transmitting, through the at least onetransceiver, a physical random access channel (PRACH); detectingdownlink control information (DCI) in response to the PRACH during awindow having a length exceeding 10 ms; receiving, through the at leastone transceiver, a physical downlink shared channel (PDSCH) within thewindow based on the DCI, and based on the UE being incapable of checkingwhether two bits of a first system frame number (SFN) included in theDCI are the same as two bits of a second SFN in which the PRACH istransmitted: transmitting the uplink signal based on the PDSCHregardless of whether the two bits of the first SFN are the same as thetwo bits of the second SFN.
 5. The UE of claim 4, wherein based on theUE being capable of checking whether the two bits for the first SFN arethe same as the two bits of the second SFN: transmitting the uplinksignal based on the PDSCH and based on the UE confirming that the twobits of the first SFN are the same as the two bits of the second SFN. 6.The UE of claim 4, wherein the DCI is scrambled by a MsgB-Radio NetworkTemporary Identifier (RNTI).
 7. An apparatus configured to transmit anuplink signal in a wireless communication system, the apparatuscomprising: at least one processor; and at least one memory operablyconnected to the at least one processor and configured to storeinstructions that, when executed, cause the at least one processor toperform operations comprising: transmitting a physical random accesschannel (PRACH); detecting downlink control information (DCI) inresponse to the PRACH during a window having a length exceeding 10 ms;and receiving a physical downlink shared channel (PDSCH) within thewindow based on the DCI, and based on the UE being incapable of checkingwhether two bits of a first system frame number (SFN) included in theDCI are the same as two bits of a second SFN in which the PRACH istransmitted: transmitting the uplink signal based on the PDSCHregardless of whether the two bits of the first SFN are the same as thetwo bits of the second SFN.
 8. The method of claim 1, wherein the uplinksignal is a Physical Uplink Shared Channel (PUSCH) based on the PDSCHproviding a fallback Random Access Response (RAR) message.
 9. The methodof claim 1, wherein the uplink signal is a Physical Uplink ControlChannel (PUCCH) based on the PDSCH providing a success Random AccessResponse (RAR) message.
 10. The UE of claim 4, wherein the uplink signalis a Physical Uplink Shared Channel (PUSCH) based on the PDSCH providinga fallback Random Access Response (RAR) message.
 11. The UE of claim 4,wherein the uplink signal is a Physical Uplink Control Channel (PUCCH)based on the PDSCH providing a success Random Access Response (RAR)message.